Merge changes from topic "bt_a2dp_src_sink_coexist"

* changes:
  Add A2DP src and sink co-exist feature bta layer (1/5)
  Add A2DP src and sink co-exist feature btif layer (2/5)
  Add A2DP src and sink co-exist feature stack layer (3/5)
  Add A2DP src and sink co-exist feature profile/avrcp layer (4/5)
  Add A2DP src and sink co-exist feature init::flag (5/5)