Merge bitcoin/bitcoin#35914: test, fuzz: Remove unused variables

### src/test/fuzz/cluster_linearize.cpp
@@ -611,7 +611,6 @@ FUZZ_TARGET(clusterlin_components)
     // Construct a depgraph.
     SpanReader reader(buffer);
     DepGraph<TestBitSet> depgraph;
-    std::vector<DepGraphIndex> linearization;
     try {
         reader >> Using<DepGraphFormatter>(depgraph);
     } catch (const std::ios_base::failure&) {}

### src/test/fuzz/locale.cpp
@@ -45,7 +45,6 @@ FUZZ_TARGET(locale)
     const char* c_locale = std::setlocale(LC_ALL, "C");
     assert(c_locale != nullptr);
 
-    const std::string random_string = fuzzed_data_provider.ConsumeRandomLengthString(5);
     const int64_t random_int64 = fuzzed_data_provider.ConsumeIntegral<int64_t>();
     const std::string tostring_without_locale = util::ToString(random_int64);
     const std::string strprintf_int_without_locale = strprintf("%d", random_int64);

### src/test/fuzz/p2p_transport_serialization.cpp
@@ -86,7 +86,6 @@ FUZZ_TARGET(p2p_transport_serialization, .init = initialize_p2p_transport_serial
             assert(msg.m_raw_message_size == CMessageHeader::HEADER_SIZE + msg.m_message_size);
             assert(msg.m_time == time);
 
-            std::vector<unsigned char> header;
             auto msg2 = NetMsg::Make(msg.m_type, std::span{msg.m_recv});
             bool queued = send_transport.SetMessageToSend(msg2);
             assert(queued);

### src/test/rbf_tests.cpp
@@ -121,11 +121,6 @@ BOOST_FIXTURE_TEST_CASE(rbf_helper_functions, TestChain100Setup)
     BOOST_CHECK_EQUAL(entry8_high->GetFee(), high_fee);
 
     CTxMemPool::setEntries set_12_normal{entry1_normal, entry2_normal};
-    CTxMemPool::setEntries set_34_cpfp{entry3_low, entry4_high};
-    CTxMemPool::setEntries set_56_low{entry5_low, entry6_low_prioritised};
-    CTxMemPool::setEntries set_78_high{entry7_high, entry8_high};
-    CTxMemPool::setEntries all_entries{entry1_normal, entry2_normal, entry3_low, entry4_high,
-                                       entry5_low, entry6_low_prioritised, entry7_high, entry8_high};
     CTxMemPool::setEntries empty_set;
 
     const auto unused_txid = Txid::FromUint256(GetRandHash());

### src/test/txgraph_tests.cpp
@@ -290,7 +290,7 @@ BOOST_AUTO_TEST_CASE(txgraph_trim_big_singletons)
     BOOST_CHECK(graph->IsOversized(TxGraph::Level::TOP));
 
     // Call Trim() to remove transactions and bring the cluster back within limits.
-    auto removed_refs = graph->Trim();
+    graph->Trim();
     graph->SanityCheck();
     BOOST_CHECK_EQUAL(graph->GetTransactionCount(TxGraph::Level::TOP), NUM_TOTAL_TX - 6);
     BOOST_CHECK(!graph->IsOversized(TxGraph::Level::TOP));

### src/wallet/test/coinselector_tests.cpp
@@ -169,7 +169,6 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
 {
     FastRandomContext rand{};
     // Setup
-    std::vector<COutput> utxo_pool;
     SelectionResult expected_result(CAmount(0), SelectionAlgorithm::BNB);
     size_t expected_attempts;
 

### src/wallet/test/util.cpp
@@ -67,7 +67,6 @@ std::shared_ptr<CWallet> TestCreateWallet(WalletContext& context)
     options.create_flags = WALLET_FLAG_DESCRIPTORS;
     DatabaseStatus status;
     bilingual_str error;
-    std::vector<bilingual_str> warnings;
     auto database = MakeWalletDatabase("", options, status, error);
     return TestCreateWallet(std::move(database), context, options.create_flags);
 }
@@ -91,7 +90,6 @@ std::shared_ptr<CWallet> TestLoadWallet(WalletContext& context)
     options.require_existing = true;
     DatabaseStatus status;
     bilingual_str error;
-    std::vector<bilingual_str> warnings;
     auto database = MakeWalletDatabase("", options, status, error);
     return TestLoadWallet(std::move(database), context);
 }

### src/wallet/test/wallet_tests.cpp
@@ -728,7 +728,6 @@ BOOST_FIXTURE_TEST_CASE(RemoveTxs, TestChain100Setup)
     CKey key = GenerateRandomKey();
     AddKey(*wallet, key);
 
-    std::string error;
     m_coinbase_txns.push_back(CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey())).vtx[0]);
     auto block_tx = TestSimpleSpend(*m_coinbase_txns[0], 0, coinbaseKey, GetScriptForRawPubKey(key.GetPubKey()));
     CreateAndProcessBlock({block_tx}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));