[NATIVECPU][UR] added mutex to backend queue (#18923)

Before this PR one thread could add new events to the queue while
another removes events, both modifying and potentially corrupting
NativeCPU queue::events. This PR adds a mutex to the NativeCPU queue
handle to prevent this potential corruption.

Aims to at least fix: `SYCL/HostInteropTask/host-task-two-queues.cpp`

Author: uwedolinsky

unified-runtime/source/adapters/native_cpu/queue.hpp

@@ -27,18 +27,30 @@ struct ur_queue_handle_t_ : RefCounted {
 
   ur_context_handle_t getContext() const { return context; }
 
-  void addEvent(ur_event_handle_t event) { events.insert(event); }
+  void addEvent(ur_event_handle_t event) {
+    std::lock_guard<std::mutex> lock(mutex);
+    events.insert(event);
+  }
 
-  void removeEvent(ur_event_handle_t event) { events.erase(event); }
+  void removeEvent(ur_event_handle_t event) {
+    std::lock_guard<std::mutex> lock(mutex);
+    events.erase(event);
+  }
 
   void finish() {
+    std::unique_lock<std::mutex> lock(mutex);
     while (!events.empty()) {
       auto ev = *events.begin();
       // ur_event_handle_t_::wait removes itself from the events set in the
-      // queue
+      // queue.
+      ev->incrementReferenceCount();
+      // Unlocking mutex for removeEvent and for event callbacks that may need
+      // to acquire it.
+      lock.unlock();
       ev->wait();
+      decrementOrDelete(ev);
+      lock.lock();
     }
-    events.clear();
   }
 
   ~ur_queue_handle_t_() { finish(); }
@@ -58,4 +70,5 @@ struct ur_queue_handle_t_ : RefCounted {
   std::set<ur_event_handle_t> events;
   const bool inOrder;
   const bool profilingEnabled;
+  std::mutex mutex;
 };