x11: Don't set up frame sync fence on unsupported compositors

x11: Don't set up frame sync fence on unsupported compositors

Not all compositors support _NET_WM_FRAME_DRAWN.  In cases
where the compositor doesn't support _NET_WM_FRAME_DRAWN we don't
need to do all the fancy damage tracking and fence watching.

Furthermore, if the compositor doesn't support _NET_WM_FRAME_DRAWN,
it's possible that one frame will start before the previous frame has
made it through the pipeline, leading to a blown assertion.

This commit side-steps the unnecessary code and associated assertion
when _NET_WM_FRAME_DRAWN isn't supported.

Fixes: https://gitlab.gnome.org/GNOME/gtk/-/issues/2927