iOS Surface: properly reset some internal states when JS reloads
iOS Surface: properly reset some internal states when JS reloads

Summary:
There are a few important states that didn't reset correctly when reloading JS:
* the RCTSurfaceStage was stuck at all bits enabled, hence no further stage change happened (even though the state "reset" to `RCTSurfaceStageBridgeDidLoad`)
* the RCTSurfaceView didn't get recreated, because the _view ivar was never cleared
* similarly, the _touchHandler ivar attached to the _view was never re-setup --> all touches after JS reload were dropped before this diff

Reviewed By: mmmulani

Differential Revision: D7178038

fbshipit-source-id: ba49bc205f8bf43842471b7ab748cef8549ea212

arthuralee/react-native,pandiaraj44/react-native,exponent/react-native,hoastoolshop/react-native,facebook/react-native,myntra/react-native,myntra/react-native,myntra/react-native,janicduplessis/react-native,hoastoolshop/react-native,facebook/react-native,hammerandchisel/react-native,arthuralee/react-native,myntra/react-native,hoangpham95/react-native,facebook/react-native,arthuralee/react-native,myntra/react-native,pandiaraj44/react-native,hammerandchisel/react-native,javache/react-native,hoangpham95/react-native,exponentjs/react-native,exponentjs/react-native,myntra/react-native,janicduplessis/react-native,hoangpham95/react-native,exponentjs/react-native,javache/react-native,hoangpham95/react-native,pandiaraj44/react-native,myntra/react-native,facebook/react-native,pandiaraj44/react-native,javache/react-native,janicduplessis/react-native,exponentjs/react-native,hammerandchisel/react-native,javache/react-native,hoangpham95/react-native,javache/react-native,hoastoolshop/react-native,janicduplessis/react-native,hammerandchisel/react-native,exponentjs/react-native,hoastoolshop/react-native,exponent/react-native,facebook/react-native,exponentjs/react-native,exponent/react-native,hammerandchisel/react-native,exponent/react-native,pandiaraj44/react-native,myntra/react-native,hoastoolshop/react-native,exponentjs/react-native,hoangpham95/react-native,myntra/react-native,facebook/react-native,facebook/react-native,janicduplessis/react-native,hoangpham95/react-native,pandiaraj44/react-native,hoastoolshop/react-native,hoastoolshop/react-native,exponent/react-native,exponent/react-native,arthuralee/react-native,pandiaraj44/react-native,janicduplessis/react-native,janicduplessis/react-native,javache/react-native,facebook/react-native,facebook/react-native,exponent/react-native,hoastoolshop/react-native,arthuralee/react-native,janicduplessis/react-native,exponentjs/react-native,exponent/react-native,hoangpham95/react-native,javache/react-native,hammerandchisel/react-native,javache/react-native,hammerandchisel/react-native,javache/react-native,hammerandchisel/react-native,pandiaraj44/react-native