AVRCP Controller update loop.

The process for getting media browsing contents from a remote device
required several intents sent back and forth between the
MediaBrowserService and the AvrcpControllerService.  This required that
any application using A2dpMediaBrowserService utilized understood the
nuances of Bluetooth media browsing.  This update simplifies the
experience into two primary capabilities listing contents of a
directory, and selecting an item to play.

Bug: 79093111
Test: Browse media players via Bluetooth
Change-Id: I99ca081f6a5ef51917b8a9a9b7dac610650d6b57