Introduce PipMediaController.MetadataListener

Introduce MetadataListener interface to the PipMediaController (required
by .tv.PipNotification.
Remove unused field mActivityManager and unused IActivityManager
constructor parameter.

Bug: 169575409
Bug: 165795012
Test: make WindowManager-Shell; make SystemUI
Change-Id: I6988d9aa95edd6152d807300520803116f193a3b