Without an associated actor, or explicit frame clock set, in the future
a timeline will not know how to progress, as there will be no singe
frame clock to assume is the main one. Thus, deprecate the construction
of timelines without either an actor or frame clock set.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285
The association is inactive, as in it doesn't do anything yet, but it
will later be used to determine what frame clock should be driving the
timeline by looking at what stage view the actor is currently on.
This also adapts sub types (ClutterPropertyTransition) to have
constuctors that takes an actor just as the new ClutterTimeline
constructor.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285
