Bluetooth: AVCTP: Refactors the AVCTP to support multiple L2CAP PSMs

- This patch refactors the AVCTP layer to support multiple L2CAP PSMs
- Introduced bt_avctp_server structure for dynamic L2CAP server
  registration and new server register apis
- Added k_sem protected server list to support multiple AVCTP servers

Signed-off-by: Make Shi <make.shi@nxp.com>