[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/game/objects/structures/morgue.dm

@@ -306,7 +306,7 @@ GLOBAL_LIST_EMPTY(crematoriums)
 	layer = TRAY_LAYER
 	var/obj/structure/bodycontainer/connected = null
 	anchored = TRUE
-	pass_flags = LETPASSTHROW
+	pass_flags_self = LETPASSTHROW
 	max_integrity = 350
 
 /obj/structure/tray/Destroy()
@@ -362,17 +362,11 @@ GLOBAL_LIST_EMPTY(crematoriums)
 	name = "morgue tray"
 	desc = "Apply corpse before closing."
 	icon_state = "morguet"
+	pass_flags_self = PASSTABLE
 
-/obj/structure/tray/m_tray/CanPass(atom/movable/mover, turf/target)
-	if(istype(mover) && (mover.pass_flags & PASSTABLE))
-		return 1
+/obj/structure/tray/m_tray/CanAllowThrough(atom/movable/mover, turf/target)
+	. = ..()
+	if(.)
+		return
 	if(locate(/obj/structure/table) in get_turf(mover))
-		return 1
-	else
-		return 0
-
-/obj/structure/tray/m_tray/CanAStarPass(ID, dir, caller)
-	. = !density
-	if(ismovable(caller))
-		var/atom/movable/mover = caller
-		. = . || (mover.pass_flags & PASSTABLE)
+		return TRUE