Xwayland: implement drm-lease-v1

This commit allows X11 clients running through Xwayland to lease
non-desktop connectors from the Wayland compositor by implementing
support for drm-lease-v1.
In order to not deadlock with the Wayland compositor if its response
to a lease request is delayed, the new interface in _rrScrPriv
introduced in the last commit is used, which makes it possible to
block the X11 client while a response is pending.
Leasing normal outputs is not yet supported, all connectors offered
for lease will be advertised as non-desktop.

Co-authored-by: Xaver Hugl <xaver.hugl@gmail.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Acked-by: Olivier Fourdan <ofourdan@redhat.com>
Acked-by: Michel Dänzer <mdaenzer@redhat.com>
4 jobs for drm-lease in 2 minutes and 14 seconds (queued for 10 seconds)