[DNM][DNM][WIP] Projectile backend code port and update

Ports#54924,  #65061, #59804 from /tg.
adds auxiliary code from /tg to make code work.

code/modules/ruins/objects_and_mobs/necropolis_gate.dm

@@ -59,10 +59,10 @@
 /obj/structure/necropolis_gate/singularity_pull()
 	return 0
 
-/obj/structure/necropolis_gate/CanPass(atom/movable/mover, turf/target)
-	if(get_dir(loc, target) == dir)
-		return !density
-	return 1
+/obj/structure/necropolis_gate/CanAllowThrough(atom/movable/mover, turf/target)
+	. = ..()
+	if(!(get_dir(loc, target) == dir))
+		return TRUE
 
 /obj/structure/necropolis_gate/CheckExit(atom/movable/O, target)
 	if(get_dir(O.loc, target) == dir)