Modularize InitializeCore

Summary: Split up InitializeCore into a bunch of modules. The idea here is to make it easier for apps to just get the initialization logic they want and leave behind what they don't; for example, if you don't want the Map/Set polyfills, instead of requiring InitializeCore you can require the modules you want from it.

Reviewed By: yungsters

Differential Revision: D10842564

fbshipit-source-id: 3b12d54fddea8c4ee75886022338c214987a015c

Libraries/Core/checkNativeVersion.js

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+'use strict';
+
+/**
+ * Check for compatibility between the JS and native code.
+ * You can use this module directly, or just require InitializeCore.
+ */
+const ReactNativeVersionCheck = require('ReactNativeVersionCheck');
+ReactNativeVersionCheck.checkVersions();