refactor: Move `StdMutex` to its own header

diff --git a/src/logging.h b/src/logging.h
index e2149501..803bdac1 100644
--- a/src/logging.h
+++ b/src/logging.h
@@ -8,9 +8,9 @@
 
 #include <crypto/siphash.h>
 #include <logging/categories.h> // IWYU pragma: export
-#include <threadsafety.h>
 #include <util/fs.h>
 #include <util/log.h> // IWYU pragma: export
+#include <util/stdmutex.h>
 #include <util/string.h>
 #include <util/time.h>
 
diff --git a/src/threadsafety.h b/src/threadsafety.h
index b79d4c76..35f3b813 100644
--- a/src/threadsafety.h
+++ b/src/threadsafety.h
@@ -6,8 +6,6 @@
 #ifndef BITCOIN_THREADSAFETY_H
 #define BITCOIN_THREADSAFETY_H
 
-#include <mutex>
-
 #ifdef __clang__
 // TL;DR Add GUARDED_BY(mutex) to member variables. The others are
 // rarely necessary. Ex: int nFoo GUARDED_BY(cs_foo);
@@ -54,26 +52,4 @@
 #define ASSERT_EXCLUSIVE_LOCK(...)
 #endif // __GNUC__
 
-// StdMutex provides an annotated version of std::mutex for us,
-// and should only be used when sync.h Mutex/LOCK/etc are not usable.
-class LOCKABLE StdMutex : public std::mutex
-{
-public:
-#ifdef __clang__
-    //! For negative capabilities in the Clang Thread Safety Analysis.
-    //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
-    //! with the ! operator, to indicate that a mutex should not be held.
-    const StdMutex& operator!() const { return *this; }
-#endif // __clang__
-};
-
-// StdLockGuard provides an annotated version of std::lock_guard for us,
-// and should only be used when sync.h Mutex/LOCK/etc are not usable.
-class SCOPED_LOCKABLE StdLockGuard : public std::lock_guard<StdMutex>
-{
-public:
-    explicit StdLockGuard(StdMutex& cs) EXCLUSIVE_LOCK_FUNCTION(cs) : std::lock_guard<StdMutex>(cs) {}
-    ~StdLockGuard() UNLOCK_FUNCTION() = default;
-};
-
 #endif // BITCOIN_THREADSAFETY_H
diff --git a/src/util/stdmutex.h b/src/util/stdmutex.h
new file mode 100644
index 00000000..4c3c0cec
--- /dev/null
+++ b/src/util/stdmutex.h
@@ -0,0 +1,35 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_STDMUTEX_H
+#define BITCOIN_UTIL_STDMUTEX_H
+
+#include <threadsafety.h> // IWYU pragma: export
+
+#include <mutex>
+
+// StdMutex provides an annotated version of std::mutex for us,
+// and should only be used when sync.h Mutex/LOCK/etc are not usable.
+class LOCKABLE StdMutex : public std::mutex
+{
+public:
+#ifdef __clang__
+    //! For negative capabilities in the Clang Thread Safety Analysis.
+    //! A negative requirement uses the EXCLUSIVE_LOCKS_REQUIRED attribute, in conjunction
+    //! with the ! operator, to indicate that a mutex should not be held.
+    const StdMutex& operator!() const { return *this; }
+#endif // __clang__
+};
+
+// StdLockGuard provides an annotated version of std::lock_guard for us,
+// and should only be used when sync.h Mutex/LOCK/etc are not usable.
+class SCOPED_LOCKABLE StdLockGuard : public std::lock_guard<StdMutex>
+{
+public:
+    explicit StdLockGuard(StdMutex& cs) EXCLUSIVE_LOCK_FUNCTION(cs) : std::lock_guard<StdMutex>(cs) {}
+    ~StdLockGuard() UNLOCK_FUNCTION() = default;
+};
+
+#endif // BITCOIN_UTIL_STDMUTEX_H