audio: Drop audio-specific authorization mechanism

audio: Drop audio-specific authorization mechanism

Remove the audio-specific service authorization mechanism in favor of
using the conventional one.

The main difference is that audio profiles will be authorized
independently. Therefore a single connection might result in several
profile authorization requests to the agent (i.e. HFP, A2DP and AVRCP).

This removes any internal policy that would skip the authorization
procedure, making it simpler and more convenient for IVI use-cases.

Agents interested in simulating the old behavior are encouraged to
either set the device as trusted or just reply to the additional
authorization requests automatically without user intervention.