xwayland: Prevent nested xwl_present_for_each_frame_callback calls

It could happen with the following call path:

frame_callback
 xwl_present_frame_callback
  xwl_present_msc_bump
   xwl_present_execute
    xwl_present_flip
     xwl_window_create_frame_callback

The nested loop called xwl_present_reset_timer, which may end up calling
xorg_list_del for the entry after the one frame_callback started the
chain for. This resulted in the outer loop never terminating, because
its next element wasn't hooked up to the list anymore.

We avoid this by calling xwl_present_reset_timer as needed in
frame_callback, and bailing from xwl_window_create_frame_callback if it
was called from the former.

We also catch nested calls and FatalError if they ever happen again due
to another bug.

v2:
* Leave xwl_present_reset_timer call in xwl_present_frame_callback,
  needed if xwl_present_msc_bump didn't hook up the window to the frame
  callback list again.

Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1442

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