Speeds up area power usage handling, and apc process(). Cleans up related code (#51002)

About The Pull Request

/area/proc/usage() attempts to give list-like access to a bunch of vars. Why not make it a list instead and avoid all the proc calls? Might be room for followup here, to do something to powered(), use_power() etc.

Some legacy machinery was ignoring the default machinery use_power pulling from the machine's power channel by default

Total power usage was unused, APCs ignored it in favor of calculating it themselves :)

I also renamed the defines because they were in the danger zone of being very common words.
Changelog

cl Naksu
code: optimized area power usage calculations.
/cl

code/game/objects/structures/electricchair.dm

@@ -29,9 +29,9 @@
 	var/area/A = get_area(src)
 	if(!isarea(A))
 		return
-	if(!A.powered(EQUIP))
+	if(!A.powered(AREA_USAGE_EQUIP))
 		return
-	A.use_power(EQUIP, 5000)
+	A.use_power(AREA_USAGE_EQUIP, 5000)
 
 	flick("echair_shock", src)
 	var/datum/effect_system/spark_spread/s = new /datum/effect_system/spark_spread