Add local APC cache to /area (#61655)

About The Pull Request

for(var/obj/machinery/power/apc/APC in GLOB.apcs_list) in get_apc makes chuck norris shed a tear
Why It's Good For The Game

tears are bad
Changelog

cl
code: /area now retains a local reference to the APC in the area, if any
/cl

code/game/objects/items/apc_frame.dm

@@ -93,7 +93,7 @@
 		return
 	var/turf/T = get_turf(on_wall) //the user is not where it needs to be.
 	var/area/A = get_area(user)
-	if(A.get_apc())
+	if(A.apc)
 		to_chat(user, span_warning("This area already has an APC!"))
 		return //only one APC per area
 	if(!A.requires_power)