Turn more unmanaged global vars into GLOB (#20446)

Turned a ton of unmanaged globals into managed globals.
Refactored some UT output.
Removed some unused things, including vars.
Added a test to ensure people don't keep adding new unmanaged vars.

code/modules/random_map/drop/drop_types.dm

@@ -1,10 +1,10 @@
-var/global/list/datum/supply_drop_loot/supply_drop
+GLOBAL_LIST_INIT_TYPED(supply_drop, /datum/supply_drop_loot, null)
 
 /proc/supply_drop_random_loot_types()
-	if(!supply_drop)
-		supply_drop = init_subtypes(/datum/supply_drop_loot)
-		sortTim(supply_drop, GLOBAL_PROC_REF(cmp_supply_drop), FALSE)
-	return supply_drop
+	if(!GLOB.supply_drop)
+		GLOB.supply_drop = init_subtypes(/datum/supply_drop_loot)
+		sortTim(GLOB.supply_drop, GLOBAL_PROC_REF(cmp_supply_drop), FALSE)
+	return GLOB.supply_drop
 
 /datum/supply_drop_loot
 	var/name = ""

code/modules/random_map/mazes/maze_cell.dm

@@ -1,4 +1,4 @@
-var/maze_cell_count = 0
+GLOBAL_VAR_INIT(maze_cell_count, 0)
 
 /datum/maze_cell
 	var/name
@@ -9,8 +9,8 @@ var/maze_cell_count = 0
 	var/oy
 
 /datum/maze_cell/New(var/nx,var/ny,var/nox,var/noy)
-	maze_cell_count++
-	uid = maze_cell_count
+	GLOB.maze_cell_count++
+	uid = GLOB.maze_cell_count
 	name = "cell #[uid]"
 	x = nx
 	y = ny