Hitby refactor (#19624)

Refactored hitby to be in line with TG's version.
Refactored item weight defines to a more clear naming scheme, also in
line with TG's version.
Refactored how the movement bumps are handled, ported signals to handle
them, in preparation for the movement update.
Fixed disposal hit bouncing the hitting atom on the wall.
Items do not push other items anymore if they are tiny.

code/modules/effects/map_effects/portal.dm

@@ -51,6 +51,15 @@ when portals are shortly lived, or when portals are made to be obvious with spec
 	var/portal_distance_x = 0 // How far the portal is from the left edge, in tiles.
 	var/portal_distance_y = 0 // How far the portal is from the top edge.
 
+/obj/effect/map_effect/portal/Initialize()
+	. = ..()
+
+	var/static/list/loc_connections = list(
+		COMSIG_ATOM_ENTERED = PROC_REF(on_entered),
+	)
+
+	AddElement(/datum/element/connect_loc, loc_connections)
+
 /obj/effect/map_effect/portal/Destroy()
 	vis_contents = null
 	if(counterpart)
@@ -59,14 +68,15 @@ when portals are shortly lived, or when portals are made to be obvious with spec
 	return ..()
 
 // Called when something touches the portal, and usually teleports them to the other side.
-/obj/effect/map_effect/portal/Crossed(atom/movable/AM)
-	..()
-	if(!AM)
+/obj/effect/map_effect/portal/proc/on_entered(datum/source, atom/movable/arrived, atom/old_loc, list/atom/old_locs)
+	SIGNAL_HANDLER
+
+	if(!arrived)
 		return
 	if(!counterpart)
 		return
 
-	go_through_portal(AM)
+	go_through_portal(arrived)
 
 
 /obj/effect/map_effect/portal/proc/go_through_portal(atom/movable/AM)