Fabric: Using `executeSynchronouslyOnSameThread_CAN_DEADLOCK` in MainRunLoopEventBeat

Summary:
We are replacing inline-ed implementation with practically the same one implemented as the helper method.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D20551409

fbshipit-source-id: fcc6f497cd240af65fba534051c217fe5746ce82

React/Fabric/Utils/MainRunLoopEventBeat.mm

@@ -58,30 +58,7 @@ void MainRunLoopEventBeat::lockExecutorAndBeat() const
     return;
   }
 
-  // Note: We need the third mutex to get back to the main thread before
-  // the lambda is finished (because all mutexes are allocated on the stack).
-  std::mutex mutex1;
-  std::mutex mutex2;
-  std::mutex mutex3;
-
-  mutex1.lock();
-  mutex2.lock();
-  mutex3.lock();
-
-  jsi::Runtime *runtimePtr;
-
-  runtimeExecutor_([&](jsi::Runtime &runtime) {
-    runtimePtr = &runtime;
-    mutex1.unlock();
-    // `beat` is called somewhere here.
-    mutex2.lock();
-    mutex3.unlock();
-  });
-
-  mutex1.lock();
-  beat(*runtimePtr);
-  mutex2.unlock();
-  mutex3.lock();
+  executeSynchronouslyOnSameThread_CAN_DEADLOCK(runtimeExecutor_, [this](jsi::Runtime &runtime) { beat(runtime); });
 }
 
 } // namespace react