Merge pull request #62716 from apple/eng/PR-103426321-mutex-initialization

[Task-to-Thread] Make sure to explicitly initialize the drainLock in DefaultActorImpl::initialize

Author: rokhinip

stdlib/public/Concurrency/Actor.cpp

@@ -853,7 +853,9 @@ class DefaultActorImpl : public HeapObject {
   /// Properly construct an actor, except for the heap header.
   void initialize(bool isDistributedRemote = false) {
     this->isDistributedRemoteActor = isDistributedRemote;
-#if !SWIFT_CONCURRENCY_ACTORS_AS_LOCKS
+#if SWIFT_CONCURRENCY_ACTORS_AS_LOCKS
+    new (&this->drainLock) Mutex();
+#else
    _status().store(ActiveActorStatus(), std::memory_order_relaxed);
 #endif
     SWIFT_TASK_DEBUG_LOG("Creating default actor %p", this);