PointerEvents: RNTester make example easier to specify what events you want to listen to

Summary: Changelog: [Internal] - Make it easier to specify what events to listen to on each `EventfulView`. This is helpful for testing future optimizations to event dispatch filtering. Also removed the switches for triggering events -- the idea being that we're using these examples with Metro and we can just remove the relevant props when we want to not fire any events.

Reviewed By: kacieb

Differential Revision: D36530066

fbshipit-source-id: 3ff45c263bdcacedde8d2720e156ab8156424c53