Update SSOverlays (ported from Baystation) (#19051)

Our SSOverlays system is outdated, and is likely the cause of many of
the issues seen in #18895. It has also been linked to a massive server
performance decrease.

This brings an updated system from Baystation, hopefully with speed
increases.

Should be testmerged, ideally with #18895.

---------

Co-authored-by: Cody Brittain <cbrittain10@live.com>

code/modules/assembly/timer.dm

@@ -51,10 +51,10 @@
 			time = 10
 
 /obj/item/device/assembly/timer/update_icon()
-	cut_overlays()
+	ClearOverlays()
 	attached_overlays = list()
 	if(timing)
-		add_overlay("timer_timing")
+		AddOverlays("timer_timing")
 		attached_overlays += "timer_timing"
 	if(holder)
 		holder.update_icon()