Merge bitcoin#26189: refactor: Do not discard try_lock() return value

30cc1c6 refactor: Drop `owns_lock()` call (Hennadii Stepanov)
bff4e06 refactor: Do not discard `try_lock()` return value (Hennadii Stepanov)

Pull request description:

  Microsoft's C++ Standard Library uses the `[[nodiscard]]` attribute for `try_lock()`.
  See: https://github.com/microsoft/STL/blob/main/stl/inc/mutex

  This change allows to drop the current suppression for the warning C4838 and helps to prevent the upcoming warning C4858.
  See: microsoft/STL@539c26c

  Fixes bitcoin#26017.

  Split from bitcoin#25819.

ACKs for top commit:
  vasild:
    ACK 30cc1c6

Tree-SHA512: ce17404e1c78af4f763129753caf8e5a0e1c91ba398778fe912f9fcc56a847e8112460d1a1a35bf905a593b7d8e0b16c6b099ad74976b67dca5f4f3eda6ff621

Author: fanquake

src/sync.h

@@ -165,11 +165,11 @@ class SCOPED_LOCKABLE UniqueLock : public Base
     bool TryEnter(const char* pszName, const char* pszFile, int nLine)
     {
         EnterCritical(pszName, pszFile, nLine, Base::mutex(), true);
-        Base::try_lock();
-        if (!Base::owns_lock()) {
-            LeaveCritical();
+        if (Base::try_lock()) {
+            return true;
         }
-        return Base::owns_lock();
+        LeaveCritical();
+        return false;
     }
 
 public: