Upgrade example app to 0.62.0-rc.3

Summary:
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1. Remove entire `react-native/ReactNativeExampleFlipper` folder
2. Run `npx react-native init --version 0.62.0-rc.3 ReactNativeExampleFlipper`
4. restore the `package.json` and `TicTacToe` file and import
5. removed `.eslintrc`, `_BUCK` and `build_defz.bzl`, `.watchmenconfig`

Added comments below to highlight the non-generated changes

Reviewed By: passy

Differential Revision: D20221558

fbshipit-source-id: da1c895a2b0e7ce48092e64cdb5ffdb9e4a1a10b

react-native/ReactNativeFlipperExample/__tests__/App-test.js

@@ -0,0 +1,19 @@
+/**
+ * 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.
+ *
+ * @format
+ */
+
+import 'react-native';
+import React from 'react';
+import App from '../App';
+
+// Note: test renderer must be required after react-native.
+import renderer from 'react-test-renderer';
+
+it('renders correctly', () => {
+  renderer.create(<App />);
+});