Coding - Replace Standard_Mutex with std::mutex and migrate to RAII locks (#766)

- Replace legacy Standard_Mutex usage across many modules with std::mutex.
- Include <mutex> where needed and remove <Standard_Mutex.hxx> includes.
- Replace Standard_Mutex::Sentry / explicit Lock/Unlock with std::lock_guard or std::unique_lock.
- Convert optional/heap mutex holders to std::unique_ptr<std::mutex> and adapt locking accordingly.
- Simplify several singleton initializations (remove manual double-checked locking where safe).
- Use thread_local for per-thread flags instead of ad-hoc mutex protection.
- Fix BVH_BuildQueue Fetch logic to preserve thread counters and wasBusy handling.
- Remove obsolete TopTools_MutexForShapeProvider sources and update FILES.cmake.

This modernizes mutex usage, reduces dependency on custom mutex types and improves clarity of locking patterns.

src/ModelingAlgorithms/TKTopAlgo/BRepCheck/BRepCheck_Edge.cxx

@@ -259,7 +259,8 @@ void BRepCheck_Edge::InContext(const TopoDS_Shape& S)
 {
   Handle(BRepCheck_HListOfStatus) aHList;
   {
-    Standard_Mutex::Sentry aLock(myMutex.get());
+    std::unique_lock<std::mutex> aLock =
+      myMutex ? std::unique_lock<std::mutex>(*myMutex) : std::unique_lock<std::mutex>();
     if (myMap.IsBound(S))
     {
       return;
@@ -327,7 +328,7 @@ void BRepCheck_Edge::InContext(const TopoDS_Shape& S)
 
         BRep_ListIteratorOfListOfCurveRepresentation itcr(TE->Curves());
         constexpr Standard_Real                      eps           = Precision::PConfusion();
-        Standard_Boolean                             toRunParallel = !myMutex.IsNull();
+        const Standard_Boolean                       toRunParallel = myMutex != nullptr;
         while (itcr.More())
         {
           const Handle(BRep_CurveRepresentation)& cr = itcr.Value();
@@ -571,7 +572,8 @@ Standard_Boolean BRepCheck_Edge::GeometricControls() const
 
 void BRepCheck_Edge::SetStatus(const BRepCheck_Status theStatus)
 {
-  Standard_Mutex::Sentry aLock(myMutex.get());
+  std::unique_lock<std::mutex> aLock =
+    myMutex ? std::unique_lock<std::mutex>(*myMutex) : std::unique_lock<std::mutex>();
   BRepCheck::Add(*myMap(myShape), theStatus);
 }