Resolve Paper leak on Android

Summary:
On Android Paper UIManager, when calling `ReactRootView.unmountReactApplication`, the ReactRootView tag is unset [here](https://github.com/facebook/react-native/blob/main/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java#L926), before the round trip unmount operation to JS makes it's way back to a `dropView` call on `NativeViewHierarchyManager`.

In practice, this means that legacy architecture apps that unmount surfaces via `ReactRootView.unmountReactApplication` leak references to Views, and the "finalization" step (`onDropViewInstance`) is not universally called.

This fixes the issue on Paper by temporarily resetting the `ReactRootView` tag before calling `dropView`.

## Changelog

[Android][Fixed] Fix issue where `onDropViewInstance` cleanup was not being handled after `ReactRootView.unmountReactApplication`

Differential Revision: D64054042

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

@@ -672,7 +672,14 @@ public synchronized void removeRootView(int rootViewTag) {
           "View with tag " + rootViewTag + " is not registered as a root view");
     }
     View rootView = mTagsToViews.get(rootViewTag);
+    Boolean wasRootTagUnset = rootView.getId() == View.NO_ID;
+    if (wasRootTagUnset) {
+      rootView.setId(rootViewTag);
+    }
     dropView(rootView);
+    if (wasRootTagUnset) {
+      rootView.setId(View.NO_ID);
+    }
     mRootTags.delete(rootViewTag);
   }