Abort render node diffing once the cairo region reaches N rectangles
We currently only abort the render node diffing if diffing two container nodes reaches a certain maximum cost. However, that's not enough.
gtk4-demo --run=listbox and enable the layout overlay in the inspector. Scrolling the listbox now is incredibly slow and all the time is spent diffing the render nodes.
The resulting cairo region ends up with rougly 40 thousand rectangles.