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/admin/secrets/admin_secrets/alter_narsie.dm

@@ -8,7 +8,7 @@
 	var/choice = input(user, "How do you wish for Nar-Sie to interact with its surroundings?") as null|anything in list("CultStation13", "Nar-Singulo")
 	if(choice == "CultStation13")
 		log_and_message_admins("has set narsie's behaviour to \"CultStation13\".", user)
-		narsie_behaviour = choice
+		GLOB.narsie_behaviour = choice
 	if(choice == "Nar-Singulo")
 		log_and_message_admins("has set narsie's behaviour to \"Nar-Singulo\".", user)
-		narsie_behaviour = choice
+		GLOB.narsie_behaviour = choice

code/modules/admin/secrets/random_events/trigger_cordical_borer_infestation.dm

@@ -4,4 +4,4 @@
 /datum/admin_secret_item/random_event/trigger_cordical_borer_infestation/execute(var/mob/user)
 	. = ..()
 	if(.)
-		return borers.attempt_random_spawn()
+		return GLOB.borers.attempt_random_spawn()