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Our SSOverlays system is outdated, and is likely the cause of many of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/holodeck/HolodeckObjects.dm

@@ -100,7 +100,7 @@
 	I.plane = DUST_PLANE
 	I.alpha = 80
 	I.blend_mode = BLEND_ADD
-	add_overlay(I)
+	AddOverlays(I)
 
 /turf/simulated/floor/holofloor/beach
 	desc = "Uncomfortably gritty for a hologram."
@@ -143,7 +143,7 @@
 /turf/simulated/floor/holofloor/desert/Initialize()
 	. = ..()
 	if(prob(10))
-		add_overlay("asteroid[rand(0,9)]")
+		AddOverlays("asteroid[rand(0,9)]")
 
 /obj/structure/holostool
 	name = "stool"