refactor: Move `transaction_identifier.h` to primitives

diff --git a/src/index/txindex.cpp b/src/index/txindex.cpp
index 2a7c0066..11dd856e 100644
--- a/src/index/txindex.cpp
+++ b/src/index/txindex.cpp
@@ -9,7 +9,7 @@
 #include <index/disktxpos.h>
 #include <logging.h>
 #include <node/blockstorage.h>
-#include <util/transaction_identifier.h>
+#include <primitives/transaction_identifier.h>
 #include <validation.h>
 
 constexpr uint8_t DB_TXINDEX{'t'};
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index 94869aff..412cbb61 100644
--- a/src/interfaces/wallet.h
+++ b/src/interfaces/wallet.h
@@ -9,12 +9,12 @@
 #include <common/signmessage.h>
 #include <consensus/amount.h>
 #include <interfaces/chain.h>
+#include <primitives/transaction_identifier.h>
 #include <pubkey.h>
 #include <script/script.h>
 #include <support/allocators/secure.h>
 #include <util/fs.h>
 #include <util/result.h>
-#include <util/transaction_identifier.h>
 #include <util/ui_change_type.h>
 
 #include <cstdint>
diff --git a/src/merkleblock.h b/src/merkleblock.h
index 8f1d45a3..a7b37d3b 100644
--- a/src/merkleblock.h
+++ b/src/merkleblock.h
@@ -8,9 +8,9 @@
 
 #include <common/bloom.h>
 #include <primitives/block.h>
+#include <primitives/transaction_identifier.h>
 #include <serialize.h>
 #include <uint256.h>
-#include <util/transaction_identifier.h>
 
 #include <set>
 #include <vector>
diff --git a/src/primitives/transaction.cpp b/src/primitives/transaction.cpp
index fab5c407..e80ab60f 100644
--- a/src/primitives/transaction.cpp
+++ b/src/primitives/transaction.cpp
@@ -8,11 +8,11 @@
 #include <consensus/amount.h>
 #include <crypto/hex_base.h>
 #include <hash.h>
+#include <primitives/transaction_identifier.h>
 #include <script/script.h>
 #include <serialize.h>
 #include <tinyformat.h>
 #include <uint256.h>
-#include <util/transaction_identifier.h>
 
 #include <algorithm>
 #include <cassert>
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index c5d27591..295bce61 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -8,10 +8,10 @@
 
 #include <attributes.h>
 #include <consensus/amount.h>
+#include <primitives/transaction_identifier.h> // IWYU pragma: export
 #include <script/script.h>
 #include <serialize.h>
 #include <uint256.h>
-#include <util/transaction_identifier.h> // IWYU pragma: export
 
 #include <cstddef>
 #include <cstdint>
diff --git a/src/primitives/transaction_identifier.h b/src/primitives/transaction_identifier.h
new file mode 100644
index 00000000..b753c1df
--- /dev/null
+++ b/src/primitives/transaction_identifier.h
@@ -0,0 +1,94 @@
+// Copyright (c) 2023-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://opensource.org/license/mit.
+
+#ifndef BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H
+#define BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H
+
+#include <attributes.h>
+#include <uint256.h>
+#include <util/types.h>
+
+#include <compare>
+#include <concepts>
+#include <tuple>
+#include <variant>
+
+/** transaction_identifier represents the two canonical transaction identifier
+ * types (txid, wtxid).*/
+template <bool has_witness>
+class transaction_identifier
+{
+    uint256 m_wrapped;
+
+    // Note: Use FromUint256 externally instead.
+    transaction_identifier(const uint256& wrapped) : m_wrapped{wrapped} {}
+
+    constexpr int Compare(const transaction_identifier<has_witness>& other) const { return m_wrapped.Compare(other.m_wrapped); }
+    template <typename Other>
+    constexpr int Compare(const Other& other) const
+    {
+        static_assert(ALWAYS_FALSE<Other>, "Forbidden comparison type");
+        return 0;
+    }
+
+public:
+    transaction_identifier() : m_wrapped{} {}
+
+    template <typename Other>
+    bool operator==(const Other& other) const { return Compare(other) == 0; }
+    template <typename Other>
+    bool operator!=(const Other& other) const { return Compare(other) != 0; }
+    template <typename Other>
+    bool operator<(const Other& other) const { return Compare(other) < 0; }
+
+    const uint256& ToUint256() const LIFETIMEBOUND { return m_wrapped; }
+    static transaction_identifier FromUint256(const uint256& id) { return {id}; }
+
+    /** Wrapped `uint256` methods. */
+    constexpr bool IsNull() const { return m_wrapped.IsNull(); }
+    constexpr void SetNull() { m_wrapped.SetNull(); }
+    static std::optional<transaction_identifier> FromHex(std::string_view hex)
+    {
+        auto u{uint256::FromHex(hex)};
+        if (!u) return std::nullopt;
+        return FromUint256(*u);
+    }
+    std::string GetHex() const { return m_wrapped.GetHex(); }
+    std::string ToString() const { return m_wrapped.ToString(); }
+    static constexpr auto size() { return decltype(m_wrapped)::size(); }
+    constexpr const std::byte* data() const { return reinterpret_cast<const std::byte*>(m_wrapped.data()); }
+    constexpr const std::byte* begin() const { return reinterpret_cast<const std::byte*>(m_wrapped.begin()); }
+    constexpr const std::byte* end() const { return reinterpret_cast<const std::byte*>(m_wrapped.end()); }
+    template <typename Stream> void Serialize(Stream& s) const { m_wrapped.Serialize(s); }
+    template <typename Stream> void Unserialize(Stream& s) { m_wrapped.Unserialize(s); }
+};
+
+/** Txid commits to all transaction fields except the witness. */
+using Txid = transaction_identifier<false>;
+/** Wtxid commits to all transaction fields including the witness. */
+using Wtxid = transaction_identifier<true>;
+
+template <typename T>
+concept TxidOrWtxid = std::is_same_v<T, Txid> || std::is_same_v<T, Wtxid>;
+
+class GenTxid : public std::variant<Txid, Wtxid>
+{
+public:
+    using variant::variant;
+
+    bool IsWtxid() const { return std::holds_alternative<Wtxid>(*this); }
+
+    const uint256& ToUint256() const LIFETIMEBOUND
+    {
+        return std::visit([](const auto& id) -> const uint256& { return id.ToUint256(); }, *this);
+    }
+
+    friend auto operator<=>(const GenTxid& a, const GenTxid& b)
+    {
+        // Use a reference for read-only access to the hash, avoiding a copy that might not be optimized away.
+        return std::tuple<bool, const uint256&>(a.IsWtxid(), a.ToUint256()) <=> std::tuple<bool, const uint256&>(b.IsWtxid(), b.ToUint256());
+    }
+};
+
+#endif // BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H
diff --git a/src/qt/sendcoinsdialog.h b/src/qt/sendcoinsdialog.h
index adb8e7fc..4d5adc4f 100644
--- a/src/qt/sendcoinsdialog.h
+++ b/src/qt/sendcoinsdialog.h
@@ -5,9 +5,9 @@
 #ifndef BITCOIN_QT_SENDCOINSDIALOG_H
 #define BITCOIN_QT_SENDCOINSDIALOG_H
 
+#include <primitives/transaction_identifier.h>
 #include <qt/clientmodel.h>
 #include <qt/walletmodel.h>
-#include <util/transaction_identifier.h>
 
 #include <QDialog>
 #include <QMessageBox>
diff --git a/src/qt/transactionrecord.h b/src/qt/transactionrecord.h
index fc28fc3e..2c5d834b 100644
--- a/src/qt/transactionrecord.h
+++ b/src/qt/transactionrecord.h
@@ -6,8 +6,8 @@
 #define BITCOIN_QT_TRANSACTIONRECORD_H
 
 #include <consensus/amount.h>
+#include <primitives/transaction_identifier.h>
 #include <uint256.h>
-#include <util/transaction_identifier.h>
 
 #include <QList>
 #include <QString>
diff --git a/src/qt/transactionview.h b/src/qt/transactionview.h
index bff1b198..d661d9b6 100644
--- a/src/qt/transactionview.h
+++ b/src/qt/transactionview.h
@@ -7,8 +7,8 @@
 
 #include <qt/guiutil.h>
 
+#include <primitives/transaction_identifier.h>
 #include <uint256.h>
-#include <util/transaction_identifier.h>
 
 #include <QWidget>
 #include <QKeyEvent>
diff --git a/src/qt/walletmodel.h b/src/qt/walletmodel.h
index bcdd6dbd..ece797bf 100644
--- a/src/qt/walletmodel.h
+++ b/src/qt/walletmodel.h
@@ -10,8 +10,8 @@
 #include <qt/walletmodeltransaction.h>
 
 #include <interfaces/wallet.h>
+#include <primitives/transaction_identifier.h>
 #include <support/allocators/secure.h>
-#include <util/transaction_identifier.h>
 
 #include <vector>
 
diff --git a/src/test/fuzz/hex.cpp b/src/test/fuzz/hex.cpp
index 64c75304..e2d08ac2 100644
--- a/src/test/fuzz/hex.cpp
+++ b/src/test/fuzz/hex.cpp
@@ -4,13 +4,13 @@
 
 #include <core_io.h>
 #include <primitives/block.h>
+#include <primitives/transaction_identifier.h>
 #include <pubkey.h>
 #include <rpc/util.h>
 #include <test/fuzz/fuzz.h>
 #include <uint256.h>
 #include <univalue.h>
 #include <util/strencodings.h>
-#include <util/transaction_identifier.h>
 
 #include <algorithm>
 #include <cassert>
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
index 5f03641e..cd178d26 100644
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -16,6 +16,7 @@
 #include <key.h>
 #include <policy/policy.h>
 #include <policy/settings.h>
+#include <primitives/transaction_identifier.h>
 #include <script/script.h>
 #include <script/script_error.h>
 #include <script/sigcache.h>
@@ -29,7 +30,6 @@
 #include <test/util/transaction_utils.h>
 #include <util/strencodings.h>
 #include <util/string.h>
-#include <util/transaction_identifier.h>
 #include <validation.h>
 
 #include <functional>
diff --git a/src/test/uint256_tests.cpp b/src/test/uint256_tests.cpp
index de75c5c7..80e10104 100644
--- a/src/test/uint256_tests.cpp
+++ b/src/test/uint256_tests.cpp
@@ -2,11 +2,11 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <primitives/transaction_identifier.h>
 #include <streams.h>
 #include <test/util/setup_common.h>
 #include <uint256.h>
 #include <util/strencodings.h>
-#include <util/transaction_identifier.h>
 
 #include <boost/test/unit_test.hpp>
 
diff --git a/src/txmempool.h b/src/txmempool.h
index 5c81876a..f471726c 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -17,12 +17,12 @@
 #include <policy/feerate.h>
 #include <policy/packages.h>
 #include <primitives/transaction.h>
+#include <primitives/transaction_identifier.h>
 #include <sync.h>
 #include <util/epochguard.h>
 #include <util/feefrac.h>
 #include <util/hasher.h>
 #include <util/result.h>
-#include <util/transaction_identifier.h>
 
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/identity.hpp>
diff --git a/src/util/transaction_identifier.h b/src/util/transaction_identifier.h
deleted file mode 100644
index b59f2e77..00000000
--- a/src/util/transaction_identifier.h
+++ /dev/null
@@ -1,94 +0,0 @@
-// Copyright (c) 2023-present The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or https://opensource.org/license/mit.
-
-#ifndef BITCOIN_UTIL_TRANSACTION_IDENTIFIER_H
-#define BITCOIN_UTIL_TRANSACTION_IDENTIFIER_H
-
-#include <attributes.h>
-#include <uint256.h>
-#include <util/types.h>
-
-#include <compare>
-#include <concepts>
-#include <tuple>
-#include <variant>
-
-/** transaction_identifier represents the two canonical transaction identifier
- * types (txid, wtxid).*/
-template <bool has_witness>
-class transaction_identifier
-{
-    uint256 m_wrapped;
-
-    // Note: Use FromUint256 externally instead.
-    transaction_identifier(const uint256& wrapped) : m_wrapped{wrapped} {}
-
-    constexpr int Compare(const transaction_identifier<has_witness>& other) const { return m_wrapped.Compare(other.m_wrapped); }
-    template <typename Other>
-    constexpr int Compare(const Other& other) const
-    {
-        static_assert(ALWAYS_FALSE<Other>, "Forbidden comparison type");
-        return 0;
-    }
-
-public:
-    transaction_identifier() : m_wrapped{} {}
-
-    template <typename Other>
-    bool operator==(const Other& other) const { return Compare(other) == 0; }
-    template <typename Other>
-    bool operator!=(const Other& other) const { return Compare(other) != 0; }
-    template <typename Other>
-    bool operator<(const Other& other) const { return Compare(other) < 0; }
-
-    const uint256& ToUint256() const LIFETIMEBOUND { return m_wrapped; }
-    static transaction_identifier FromUint256(const uint256& id) { return {id}; }
-
-    /** Wrapped `uint256` methods. */
-    constexpr bool IsNull() const { return m_wrapped.IsNull(); }
-    constexpr void SetNull() { m_wrapped.SetNull(); }
-    static std::optional<transaction_identifier> FromHex(std::string_view hex)
-    {
-        auto u{uint256::FromHex(hex)};
-        if (!u) return std::nullopt;
-        return FromUint256(*u);
-    }
-    std::string GetHex() const { return m_wrapped.GetHex(); }
-    std::string ToString() const { return m_wrapped.ToString(); }
-    static constexpr auto size() { return decltype(m_wrapped)::size(); }
-    constexpr const std::byte* data() const { return reinterpret_cast<const std::byte*>(m_wrapped.data()); }
-    constexpr const std::byte* begin() const { return reinterpret_cast<const std::byte*>(m_wrapped.begin()); }
-    constexpr const std::byte* end() const { return reinterpret_cast<const std::byte*>(m_wrapped.end()); }
-    template <typename Stream> void Serialize(Stream& s) const { m_wrapped.Serialize(s); }
-    template <typename Stream> void Unserialize(Stream& s) { m_wrapped.Unserialize(s); }
-};
-
-/** Txid commits to all transaction fields except the witness. */
-using Txid = transaction_identifier<false>;
-/** Wtxid commits to all transaction fields including the witness. */
-using Wtxid = transaction_identifier<true>;
-
-template <typename T>
-concept TxidOrWtxid = std::is_same_v<T, Txid> || std::is_same_v<T, Wtxid>;
-
-class GenTxid : public std::variant<Txid, Wtxid>
-{
-public:
-    using variant::variant;
-
-    bool IsWtxid() const { return std::holds_alternative<Wtxid>(*this); }
-
-    const uint256& ToUint256() const LIFETIMEBOUND
-    {
-        return std::visit([](const auto& id) -> const uint256& { return id.ToUint256(); }, *this);
-    }
-
-    friend auto operator<=>(const GenTxid& a, const GenTxid& b)
-    {
-        // Use a reference for read-only access to the hash, avoiding a copy that might not be optimized away.
-        return std::tuple<bool, const uint256&>(a.IsWtxid(), a.ToUint256()) <=> std::tuple<bool, const uint256&>(b.IsWtxid(), b.ToUint256());
-    }
-};
-
-#endif // BITCOIN_UTIL_TRANSACTION_IDENTIFIER_H
diff --git a/src/wallet/receive.h b/src/wallet/receive.h
index b995e21c..f129c195 100644
--- a/src/wallet/receive.h
+++ b/src/wallet/receive.h
@@ -6,7 +6,7 @@
 #define BITCOIN_WALLET_RECEIVE_H
 
 #include <consensus/amount.h>
-#include <util/transaction_identifier.h>
+#include <primitives/transaction_identifier.h>
 #include <wallet/transaction.h>
 #include <wallet/types.h>
 #include <wallet/wallet.h>
diff --git a/src/wallet/rpc/transactions.cpp b/src/wallet/rpc/transactions.cpp
index 69c5e011..b58d3dad 100644
--- a/src/wallet/rpc/transactions.cpp
+++ b/src/wallet/rpc/transactions.cpp
@@ -5,9 +5,9 @@
 #include <core_io.h>
 #include <key_io.h>
 #include <policy/rbf.h>
+#include <primitives/transaction_identifier.h>
 #include <rpc/util.h>
 #include <rpc/blockchain.h>
-#include <util/transaction_identifier.h>
 #include <util/vector.h>
 #include <wallet/receive.h>
 #include <wallet/rpc/util.h>
diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp
index 4ae34d0b..8ff89600 100644
--- a/src/wallet/spend.cpp
+++ b/src/wallet/spend.cpp
@@ -13,6 +13,7 @@
 #include <numeric>
 #include <policy/policy.h>
 #include <primitives/transaction.h>
+#include <primitives/transaction_identifier.h>
 #include <script/script.h>
 #include <script/signingprovider.h>
 #include <script/solver.h>
@@ -21,7 +22,6 @@
 #include <util/rbf.h>
 #include <util/trace.h>
 #include <util/translation.h>
-#include <util/transaction_identifier.h>
 #include <wallet/coincontrol.h>
 #include <wallet/fees.h>
 #include <wallet/receive.h>
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 95ed7af8..f39df174 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -15,6 +15,7 @@
 #include <outputtype.h>
 #include <policy/feerate.h>
 #include <primitives/transaction.h>
+#include <primitives/transaction_identifier.h>
 #include <script/interpreter.h>
 #include <script/script.h>
 #include <support/allocators/secure.h>
@@ -26,7 +27,6 @@
 #include <util/result.h>
 #include <util/string.h>
 #include <util/time.h>
-#include <util/transaction_identifier.h>
 #include <util/ui_change_type.h>
 #include <wallet/crypter.h>
 #include <wallet/db.h>
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 2c0073f3..773f65ca 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -9,6 +9,7 @@
 
 #include <common/system.h>
 #include <key_io.h>
+#include <primitives/transaction_identifier.h>
 #include <protocol.h>
 #include <script/script.h>
 #include <serialize.h>
@@ -16,7 +17,6 @@
 #include <util/bip32.h>
 #include <util/check.h>
 #include <util/fs.h>
-#include <util/transaction_identifier.h>
 #include <util/time.h>
 #include <util/translation.h>
 #include <wallet/migrate.h>
diff --git a/src/wallet/walletdb.h b/src/wallet/walletdb.h
index 5327a2cf..771d3a37 100644
--- a/src/wallet/walletdb.h
+++ b/src/wallet/walletdb.h
@@ -7,8 +7,8 @@
 #define BITCOIN_WALLET_WALLETDB_H
 
 #include <key.h>
+#include <primitives/transaction_identifier.h>
 #include <script/sign.h>
-#include <util/transaction_identifier.h>
 #include <wallet/db.h>
 #include <wallet/walletutil.h>