[MIRROR] Refactors area stuff (#265)

* Refactors area stuff (#52751)

-bitfielded a bunch of bools on /area, I left some untouched cus they get called a lot
-Unused vars
-Fixed a var pretending to be a fake bool
-Probably more

* Refactors area stuff

Co-authored-by: TiviPlus <57223640+TiviPlus@users.noreply.github.com>

code/modules/mob/dead/observer/observer.dm

@@ -409,7 +409,7 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	var/list/filtered = list()
 	for(var/V in GLOB.sortedAreas)
 		var/area/A = V
-		if(!A.hidden)
+		if(!(A.area_flags & HIDDEN_AREA))
 			filtered += A
 	var/area/thearea  = input("Area to jump to", "BOOYEA") as null|anything in filtered