ClutterFrame aims to carry information valid during dispatching a frame.
A frame may or may not include redrawing, but will always end with a
result.
A asynchronous page flip, for example, will result in a
CLUTTER_FRAME_RESULT_PENDING_PRESENTED, while a frame that only
dispatched events etc will result in CLUTTER_FRAME_RESULT_IDLE. Instead
of this being implicit, make the ClutterStageWindow implementation
handle this itself.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
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