Add missing codec initialization for A2DP Sink

Also:
 * Added missing assert to check when local codecs are not initialized
 * Removed unnecessary local copy: BtifAvSource::codec_priorities_

Bug: 74079615
Test: Manual: Enable A2DP Sink profile and initiate the connection from
      Remote A2DP Source
Change-Id: I40ea1aa2164612bbe108ac06be7f6cae8be30a72