Changes all cases of update_icons(), updateicon(), UpdateIcon() etc. to update_icon(). (#9432)

update_icons(), UpdateIcon() and updateicon() are now changed to be update_icon().

Many interactions expect a target to have an update_icon(), so they should all be the same.

Also fixed some stuff that was using relative pathing, along the way.

code/game/objects/effects/chem/foam.dm

@@ -33,7 +33,7 @@
 	if(metal)
 		var/obj/structure/foamedmetal/M = new /obj/structure/foamedmetal(src.loc)
 		M.metal = metal
-		M.updateicon()
+		M.update_icon()
 	flick("[icon_state]-disolve", src)
 	QDEL_IN(src, 5)
 
@@ -143,7 +143,7 @@
 	set_opacity(0)
 	return ..()
 
-/obj/structure/foamedmetal/proc/updateicon()
+/obj/structure/foamedmetal/update_icon()
 	if(metal == 1)
 		icon_state = "metalfoam"
 	else