Register AudioControl HAL with automotive watchdog

For now, this is a dummy implementation that registers the service
but always returns `true` for health status. We can augment it as
we create the gRPC server and figure out a heartbeat message or
equivalent facility on the AGL side, incl. systemd liveness monitoring.

Bug: 154262220
Test: flash, boot,
      observe logcat
      trout.audiocontrol@2.0-watchdog: Successfully registered the client to car watchdog server
Change-Id: I5ed1d261ec25d0bc3c5641f8c07c7e8f66a6dcf4