Adds ghost role eligibility to various ghost roles. (#11549)

* Added ghost role eligibility to CTF, possession, random animal

* Also added possessed blade to it.

* Also removed some extraneous dead/observer things.

* ahaha whoops

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

@@ -653,6 +653,7 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 		return 0
 
 	transfer_ckey(target, FALSE)
+	target.AddElement(/datum/element/ghost_role_eligibility)
 	target.faction = list("neutral")
 	return 1
 

code/modules/mob/living/simple_animal/hostile/mining_mobs/elites/elite.dm

@@ -161,7 +161,7 @@ While using this makes the system rely on OnFire, it still gives options for tim
 				INVOKE_ASYNC(src, .proc/arena_checks)
 			if(TUMOR_INACTIVE)
 				activity = TUMOR_ACTIVE
-				var/mob/dead/observer/elitemind = null
+				var/mob/elitemind = null
 				visible_message("<span class='boldwarning'>[src] begins to convulse.  Your instincts tell you to step back.</span>")
 				activator = user
 				if(!boosted)

code/modules/mob/mob_helpers.dm

@@ -443,10 +443,10 @@ It's fairly easy to fix if dealing with single letters but not so much with comp
 		var/datum/antagonist/A = M.mind.has_antag_datum(/datum/antagonist/)
 		if(A)
 			poll_message = "[poll_message] Status:[A.name]."
-	var/list/mob/dead/observer/candidates = pollCandidatesForMob(poll_message, ROLE_PAI, null, FALSE, 100, M)
+	var/list/mob/candidates = pollCandidatesForMob(poll_message, ROLE_PAI, null, FALSE, 100, M)
 
 	if(LAZYLEN(candidates))
-		var/mob/dead/observer/C = pick(candidates)
+		var/mob/C = pick(candidates)
 		to_chat(M, "Your mob has been taken over by a ghost!")
 		message_admins("[key_name_admin(C)] has taken control of ([key_name_admin(M)])")
 		M.ghostize(FALSE, TRUE)