This adds feature flags if a backend supports auto rotations. While this is not
directly a function of a backend on X11 auto rotation is not tested fully yet
and there are problems with touch input. This way a client can query if auto
rotation is fully functional on a backend.
For the KWayland backend auto rotation and tablet mode information querying is
already wired up but for now deactivated until all KWin patches have been
landed.