Call stopSurface when ReactRootView is unregistered

Summary:
In the past, in Fabric (Android), we never called stopSurface. Ever! This is bad for memory and can cause other issues, so... let's not do that.

Instead, when the ReactRootView is being torn down, we check the View ID to see if it's a Fabric RootView, and if it is, we call Fabric's stopSurface method.

Fabric stopSurface only has impact on (1) Fabric mount instructions being executed after that point and (2) tells JS to stop running the surface, on the JS thread, asynchronously.

Anecdotally it looks like all the MountItems involved in deleting and removing views from the hierarchy are executed before stopSurface is called.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D21965837

fbshipit-source-id: 5169c5a1e339fd9e016ae1234d8389b2bd30be70

ReactAndroid/src/main/java/com/facebook/react/uimanager/UIManagerModule.java

@@ -437,6 +437,11 @@ public class UIManagerModule extends ReactContextBaseJavaModule
     throw new UnsupportedOperationException();
   }
 
+  @Override
+  public void stopSurface(final int surfaceId) {
+    throw new UnsupportedOperationException();
+  }
+
   /** Unregisters a new root view. */
   @ReactMethod
   public void removeRootView(int rootViewTag) {