Bools and returns super-pr (#53221)

Replaces like 70-80% of 0 and such, as a side effect cleaned up a bunch of returns
Edit: Most left out ones are in mecha which should be done in mecha refactor already
Oh my look how clean it is

Co-authored-by: TiviPlus <TiviPlus>
Co-authored-by: Couls <coul422@gmail.com>

code/modules/spells/spell.dm

@@ -506,8 +506,8 @@ GLOBAL_LIST_INIT(spells, typesof(/obj/effect/proc_holder/spell)) //needed for th
 
 /obj/effect/proc_holder/spell/proc/can_be_cast_by(mob/caster)
 	if((human_req || clothes_req) && !ishuman(caster))
-		return 0
-	return 1
+		return FALSE
+	return TRUE
 
 /obj/effect/proc_holder/spell/targeted/proc/los_check(mob/A,mob/B)
 	//Checks for obstacles from A to B
@@ -517,9 +517,9 @@ GLOBAL_LIST_INIT(spells, typesof(/obj/effect/proc_holder/spell)) //needed for th
 		for(var/atom/movable/AM in turf)
 			if(!AM.CanPass(dummy,turf,1))
 				qdel(dummy)
-				return 0
+				return FALSE
 	qdel(dummy)
-	return 1
+	return TRUE
 
 /obj/effect/proc_holder/spell/proc/can_cast(mob/user = usr)
 	if(((!user.mind) || !(src in user.mind.spell_list)) && !(src in user.mob_spell_list))