This implements the explicit sync protocol linux-drm-syncobj-v1. This
works by importing a DRM syncobj timeline and importing/exporting fds
to/from the sync points on the timeline corresponding to buffer acquire
and release. We take fds for sync points provided during a surface
commit and use them to delay transaction application, and fetch fds
from Cogl to signal when we are done using a particular buffer.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3300>
