Fix possible deadlock in dispatchViewUpdates (#43643)

Summary:
In AppAndFlow/react-native-safe-area-context#448 it was noticed that from 0.72 (bc766ec #35889) it was possible to get a deadlock in dispatchViewUpdates. ([More details](AppAndFlow/react-native-safe-area-context#448 (comment)))

This deadlock resulted in a laggy experience for all users using https://github.com/th3rdwave/react-native-safe-area-context/ on Android.

To avoid this problem, the author of the original fix [proposed](AppAndFlow/react-native-safe-area-context#448 (comment)) this solution which was tested by Discord and many other users.

It would be great to have this backported to 0.72 and 0.73 because of the large userbase using react-native-safe-area-context since it's recommended by expo and react-navigation.

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[ANDROID] [FIXED] - Fixed possible deadlock in dispatchViewUpdates

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[ANDROID] [FIXED] - Fixed possible deadlock in dispatchViewUpdates

Pull Request resolved: #43643

Test Plan:
The original memory leak remains fixed, and can be verified in https://github.com/feiyin0719/RNMemoryLeakAndroid.

To verify the deadlock is gone, every app using https://github.com/th3rdwave/react-native-safe-area-context will work smoothly and not log any excessive `Timed out waiting for layout`
(https://github.com/17Amir17/SafeAreaContext)

Reviewed By: arushikesarwani94

Differential Revision: D55339059

Pulled By: zeyap

fbshipit-source-id: c067997364fbec734510ce99b9994e89d044384a

Author: EvertEt

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/UIImplementation.java

@@ -175,7 +175,7 @@ public void removeRootView(int rootViewTag) {
    *
    * @return The num of root view
    */
-  private int getRootViewNum() {
+  public int getRootViewNum() {
     return mOperationsQueue.getNativeViewHierarchyManager().getRootViewNum();
   }
 
@@ -608,12 +608,6 @@ public void measureLayoutRelativeToParent(
 
   /** Invoked at the end of the transaction to commit any updates to the node hierarchy. */
   public void dispatchViewUpdates(int batchId) {
-    if (getRootViewNum() <= 0) {
-      // If there are no RootViews registered, there will be no View updates to dispatch.
-      // This is a hack to prevent this from being called when Fabric is used everywhere.
-      // This should no longer be necessary in Bridgeless Mode.
-      return;
-    }
     SystraceMessage.beginSection(
             Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "UIImplementation.dispatchViewUpdates")
         .arg("batchId", batchId)

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/UIManagerModule.java

@@ -719,7 +719,12 @@ public void onBatchComplete() {
       listener.willDispatchViewUpdates(this);
     }
     try {
-      mUIImplementation.dispatchViewUpdates(batchId);
+      // If there are no RootViews registered, there will be no View updates to dispatch.
+      // This is a hack to prevent this from being called when Fabric is used everywhere.
+      // This should no longer be necessary in Bridgeless Mode.
+      if (mUIImplementation.getRootViewNum() > 0) {
+        mUIImplementation.dispatchViewUpdates(batchId);
+      }
     } finally {
       Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
     }