Track singularities in a global list (tgstation#24609)

This replaces a few operations on either the poi_list (still quite
large) or the world

code/_globalvars/lists/objects.dm

@@ -11,6 +11,7 @@ var/global/list/deliverybeacons = list()			//list of all MULEbot delivery beacon
 var/global/list/deliverybeacontags = list()			//list of all tags associated with delivery beacons.
 var/global/list/nuke_list = list()
 var/global/list/alarmdisplay = list()				//list of all machines or programs that can display station alerts
+var/global/list/singularities = list()				//list of all singularities on the station (actually technically all engines)
 
 var/global/list/chemical_reactions_list				//list of all /datum/chemical_reaction datums. Used during chemical reactions
 var/global/list/chemical_reagents_list				//list of all /datum/reagent datums indexed by reagent id. Used by chemistry stuff

code/game/gamemodes/clock_cult/clock_structures/ratvar_the_clockwork_justicar.dm

@@ -62,7 +62,7 @@
 		T.ratvar_act(1)
 	var/dir_to_step_in = pick(cardinal)
 	if(!prey)
-		for(var/obj/singularity/narsie/N in poi_list)
+		for(var/obj/singularity/narsie/N in singularities)
 			if(N.z == z)
 				prey = N
 				break

code/game/machinery/syndicatebeacon.dm

@@ -22,7 +22,7 @@
 	if(surplus() < 1500)
 		if(user) user << "<span class='notice'>The connected wire doesn't have enough current.</span>"
 		return
-	for(var/obj/singularity/singulo in poi_list)
+	for(var/obj/singularity/singulo in singularities)
 		if(singulo.z == z)
 			singulo.target = src
 	icon_state = "[icontype]1"
@@ -34,7 +34,7 @@
 
 
 /obj/machinery/power/singularity_beacon/proc/Deactivate(mob/user = null)
-	for(var/obj/singularity/singulo in poi_list)
+	for(var/obj/singularity/singulo in singularities)
 		if(singulo.target == src)
 			singulo.target = null
 	icon_state = "[icontype]0"
@@ -90,7 +90,7 @@
 			add_load(1500)
 			if(cooldown <= world.time)
 				cooldown = world.time + 100
-				for(var/obj/singularity/singulo in poi_list)
+				for(var/obj/singularity/singulo in singularities)
 					if(singulo.z == z)
 						say("The [singulo] is now [get_dist(src,singulo)] standard lengths away to the [dir2text(get_dir(src,singulo))]")
 		else

code/modules/power/singularity/field_generator.dm

@@ -319,7 +319,7 @@ field_generator power level display
 	//I want to avoid using global variables.
 	spawn(1)
 		var/temp = 1 //stops spam
-		for(var/obj/singularity/O in world)
+		for(var/obj/singularity/O in singularities)
 			if(O.last_warning && temp)
 				if((world.time - O.last_warning) > 50) //to stop message-spam
 					temp = 0

code/modules/power/singularity/singularity.dm

@@ -36,6 +36,7 @@
 	..()
 	START_PROCESSING(SSobj, src)
 	poi_list |= src
+	singularities |= src
 	for(var/obj/machinery/power/singularity_beacon/singubeacon in machines)
 		if(singubeacon.active)
 			target = singubeacon
@@ -45,6 +46,7 @@
 /obj/singularity/Destroy()
 	STOP_PROCESSING(SSobj, src)
 	poi_list.Remove(src)
+	singularities.Remove(src)
 	return ..()
 
 /obj/singularity/Move(atom/newloc, direct)