Copy shape region to Deleted

Currently, the shape region is not copied to the Deleted. If either
SurfaceItemX11 or SurfaceItemXwayland needs to build quads for a shaped
window, it won't be able to do so properly because the corresponding
x11 window is long time gone.

If the shape region changes before the window is unmapped, you may still
see visual artifacts. Unfortunately, the only way to fix that bug is to
switch to wayland.

BUG: 440001
BUG: 438458
BUG: 435378