Merge changes from topic "rfcomm_offload_socket" into main

* changes:
  Determine local mtu for offload RFCOMM socket
  Set the initial local credits to 0 for offload RFCOMM socket
  Notify offloaded RFCOMM socket channel info to socket hal
  Send signal to indicate if app is accepting incoming connection on RFCOMM listen socket
  Add RFCOMM socket offload capabilities
  Add helper functions to get RFCOMM channel and L2CAP local mtu information