Mock requireNativeComponent so manual mocking of UIManager properties isn't needed

Summary:
Fixes warnings such as `Warning: Native component for "RCTView" does not exist` when you don't mock the native view class on `UIManager`.

**Test plan (required)**

Run `npm test` with it and without it, notice that warnings are gone and results are the same.

cc cpojer
Closes https://github.com/facebook/react-native/pull/10486

Differential Revision: D4063500

Pulled By: cpojer

fbshipit-source-id: f6bdda1fdd1ad87958f435071d353684cb812af4

jest/setup.js

@@ -158,3 +158,13 @@ jest
     register: id => id,
     getByID: () => mockEmptyObject,
   }));
+
+jest.doMock('requireNativeComponent', () => {
+  const React = require('react');
+
+  return viewName => props => React.createElement(
+    viewName,
+    props,
+    props.children,
+  );
+});