Merge the overlays of windows in the overview into the WindowClone class and remove the WindowOverlay class.
Depends on !1294 (merged) (included), !1297 (merged) (included), mutter!737 (merged), mutter!1296 (merged)
Merge the overlays of windows in the overview into the WindowClone class and remove the WindowOverlay class.
Depends on !1294 (merged) (included), !1297 (merged) (included), mutter!737 (merged), mutter!1296 (merged)