Add a permission for preempting sound trigger sessions

Previously, the power to preempt sound trigger recognition sessions
for the sake of being able to capture audio on platforms that don't
support doing both concurrently, was implicitly granted based on
process (audio_server) co-location with the sound trigger service.
Since this service is now being migrated out of audio_server, a new
permission is introduced and granted to the audio server.

Change-Id: Ifcdfc2a5543d814fb0630a45cdd9bcdba4d92107
Bug: 142070343