Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
This was showing up quite high on the profiles, and there is
no real reason for copy to normalize, as the source is a
GskRoundedRect which should be normalized already unless
you did something very strange (and then you should have normalized
manually).
This is now tracking the clips added by the clip nodes.
If any particular node can't deal with a clip, it falls back to Cairo
rendering. But if it can, it will render it directly.
