Replace PlaybackActivityMonitor with AudioDeviceCallback am: e30838778e

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/MusicFX/+/22168604

Change-Id: I450e24316f451797169e436fd40f9c6c6cc2dd2f
Signed-off-by: Automerger Merge Worker <[email protected]>