Extract use of renderer to its own module

Summary:
This diff creates a proxy module to interact with the React Native renderer. The goal of this proxy is to decouple usages of several functions (e.g.: `findNodeHandle`, etc.) from the actual renderer used in an app. This way, we can easily switch between renderers without having to change code depending on it.

This will be useful to remove a specific renderer from an app bundle when it's no longer used (e.g.: Paper on the Facebook App).

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D39205975

fbshipit-source-id: 05289c0c3c8cd26d81aa1d2163097c73ec40c6ad

ReactAndroid/src/androidTest/js/UIManagerTestModule.js

@@ -10,14 +10,13 @@
 
 'use strict';
 
-const BatchedBridge = require('react-native/Libraries/BatchedBridge/BatchedBridge');
-const React = require('react');
-
-const renderApplication = require('react-native/Libraries/ReactNative/renderApplication');
-
-const {StyleSheet, Text, View} = require('react-native');
 import type {RootTag} from 'react-native/Libraries/Types/RootTagTypes';
 
+import * as React from 'react';
+import {StyleSheet, Text, View} from 'react-native';
+import BatchedBridge from 'react-native/Libraries/BatchedBridge/BatchedBridge';
+import renderApplication from 'react-native/Libraries/ReactNative/renderApplication';
+
 type FlexTestAppProps = $ReadOnly<{||}>;
 class FlexTestApp extends React.Component<FlexTestAppProps> {
   render(): React.Node {
@@ -267,4 +266,4 @@ BatchedBridge.registerCallableModule(
   UIManagerTestModule,
 );
 
-module.exports = UIManagerTestModule;
+export default UIManagerTestModule;