Fix MediaControlView2 progress bar issue

This CL does the following
1. Fix progress bar not updating issue by
   a) Removing mCurrentVisibility variable.
   b) posting progress update Runnable when playback state is
      changed.
2. Add support for hiding MediaControlView2 instance with both
   View.INVISIBLE and View.GONE inside #onVisibilityAggregated.

Bug: 73096369
Test: manually run VideoViewTest.apk
Change-Id: I9c2569e824e85c7bdd809dd4a459cf35ae1aeaa6