Bluetooth: Mesh: Add queue_size and recv_win to lpn_cb

Add Queue Size and Receive Window information to lpn
callback function to notify upper layer to determine
currently friend node information, which may be used
in future.

Add Callback structure to notification application which friendship
has been changed.

Add function `bt_mesh_friend_terminate` let's app layer determine
terminate friendship manually.

Signed-off-by: Lingao Meng <mengabc1086@gmail.com>