Refactor weather to use Z traits, assorted related cleanup (#34633)

* Add a proc for getting the station center

* Add a couple of comments to ZTRAIT defines

* Remove unused global_map list

* Refactor weather to use the trait system

* Un-hardcode the transit z-level

* Use Z traits to determine Portal Storm event areas

* Fix loading away missions containing anything that reads traits

code/game/area/areas.dm

@@ -384,9 +384,9 @@ GLOBAL_LIST_EMPTY(teleportlocs)
 			icon_state = "blue-red"
 	else
 		var/weather_icon
-		for(var/V in SSweather.existing_weather)
+		for(var/V in SSweather.processing)
 			var/datum/weather/W = V
-			if(src in W.impacted_areas)
+			if(W.stage != END_STAGE && (src in W.impacted_areas))
 				W.update_areas()
 				weather_icon = TRUE
 		if(!weather_icon)

code/game/atoms_movable.dm

@@ -657,7 +657,7 @@
 		flags_2 |= STATIONLOVING_2
 
 /atom/movable/proc/relocate()
-	var/targetturf = find_safe_turf(ZLEVEL_STATION_PRIMARY)
+	var/targetturf = find_safe_turf()
 	if(!targetturf)
 		if(GLOB.blobstart.len > 0)
 			targetturf = get_turf(pick(GLOB.blobstart))

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

@@ -330,7 +330,7 @@
 				QDEL_IN(src, 3)
 				sleep(3)
 				GLOB.clockwork_gateway_activated = TRUE
-				var/turf/T =  locate(round(world.maxx * 0.5, 1), round(world.maxy * 0.5, 1), ZLEVEL_STATION_PRIMARY) //approximate center of the station
+				var/turf/T = SSmapping.get_station_center()
 				new /obj/structure/destructible/clockwork/massive/ratvar(T)
 				SSticker.force_ending = TRUE
 				var/x0 = T.x