Initial commit of MediaPlayerWrapper

MediaPlayerWrapper is the compatibility layer for the updated AVRCP
profile. This patch implements a class that ensures that Media Updates
from a Media Player are consistent and all information is synced.

Bug: 68854188
Test: "runtest bluetooth -c com.android.bluetooth.avrcp.MediaPlayerWrapperTest"

Change-Id: If19579d77ae7a0900b08cd47be2da3065752694e