session_recovery: Add wayland extension protocol prototype for session recovery

session_recovery: Add wayland extension protocol prototype for session recovery

Like with all other wayland protocols I add the files generated with wayland
scanner here. Also the xml so we have the source around for updating and
modifications. We might want to think about wayland-scanner support in our build
system but this works for now.

The protocol prototype is hold simple and does only have a uuid signal and provide
call to handle the uuid assignment from compositor to app and app providing its
uuid if present already.