Expose PiP lifecycle callbacks to JavaScript

[jedagen]

When using iosPIP with startAutomatically, there's no way for JS to know when PiP stops. If a user dismisses or stashes PiP while backgrounded, the camera track stays published but frames stop. Remote participants see a frozen frame.

Apps need to detect this to call setCameraEnabled(false), but currently the AVPictureInPictureControllerDelegate methods in PIPController.m (lines 184, 217) only NSLog.