session: move ctrl messages from bapi to mq

session: move ctrl messages from bapi to mq

Type:refactor

Moves connect, disconnect, bind, unbind and app detach to message
queue from binary api. Simplifies app/vcl interaction with the session
layer since all session control messages are now handled over the mq.

Add/del segment messages require internal C api changes which affect all
builtin applications. They'll be moved in a different patch and might
not be back portable to 19.08.

Change-Id: I93f6d18e551b024effa75d47f5ff25f23ba8aff5
Signed-off-by: Florin Coras <[email protected]>
(cherry picked from commit 458089bbad9cf5bef6cf8119f23fc44e66b36ad3)