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/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