Summary:
**Motivation**
Fix flickering in TabBarIOS on Apple TV... issue #15081
After this change, on Apple TV, TabBarIOS item selections will be controlled purely from the native side after initial render with the `selected` prop. This is necessary because the `UITabBar` implementation in tvOS moves the selection before calling `shouldSelectViewController:`; this issue does not occur on iOS.
**Test plan**
Existing CI should still pass. Issue is resolved when testing the example code in #15081 .
Closes https://github.com/facebook/react-native/pull/15220
Differential Revision: D5601671
Pulled By: javache
fbshipit-source-id: c18e7d3482d6c07d534ff40a443a6f642d4267bb