feat(rn) remove use of externalAPIScope

Use the system broadcasting mechanism instead.

On Android I took the chance and removed the no longer needed
BaseReactView and implemented it on JitsiMeetView instead.

react/features/app/components/App.native.js

@@ -33,11 +33,6 @@ const DialogContainerWrapper = Platform.select({
  */
 type Props = AbstractAppProps & {
 
-    /**
-     * Identifier for this app on the native side.
-     */
-    externalAPIScope: string,
-
     /**
      * An object with the feature flags.
      */