Fix modsuits and defibs (#93373)

## About The Pull Request

Fixes #93359

Caused by #93165

Inventory screen elements were no longer considered reachable, which
broke mousedrop handing on objects that check "is dragging into
inventory slot"

I don't know the best way to fix this yet but I figured the next best
thing would be to make all of these use the `drag_pickup` element, which
skips this reach-ability check

Thus I refactored it slightly to accommodate for items which should
contextually not be drag-pick-up-abble and bam, works like a charm

## Changelog

🆑 Melbert
fix: Dragging defibs and modsuits off your back works again
/🆑

---------

Co-authored-by: ArcaneMusic <41715314+ArcaneMusic@users.noreply.github.com>
Co-authored-by: Xander3359 <66163761+Xander3359@users.noreply.github.com>

code/modules/projectiles/guns/energy/laser_gatling.dm

@@ -24,6 +24,7 @@
 	gun = new(src)
 	battery = new(src)
 	START_PROCESSING(SSobj, src)
+	AddElement(/datum/element/drag_pickup)
 
 /obj/item/minigunpack/Destroy()
 	if(!QDELETED(gun))
@@ -64,15 +65,6 @@
 	if(armed)
 		user.dropItemToGround(gun, TRUE)
 
-/obj/item/minigunpack/mouse_drop_dragged(atom/over_object, mob/user)
-	if(armed)
-		return
-
-	if(iscarbon(user))
-		if(istype(over_object, /atom/movable/screen/inventory/hand))
-			var/atom/movable/screen/inventory/hand/H = over_object
-			user.putItemFromInventoryInHandIfPossible(src, H.held_index)
-
 /obj/item/minigunpack/update_icon_state()
 	icon_state = armed ? "notholstered" : "holstered"
 	return ..()