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/game/objects/items/tanks/watertank.dm

@@ -28,6 +28,7 @@
 	create_reagents(volume, OPENCONTAINER)
 	noz = make_noz()
 	RegisterSignal(noz, COMSIG_MOVABLE_MOVED, PROC_REF(noz_move))
+	AddElement(/datum/element/drag_pickup)
 
 /obj/item/watertank/Destroy()
 	QDEL_NULL(noz)
@@ -90,12 +91,6 @@
 	else
 		return ..()
 
-/obj/item/watertank/mouse_drop_dragged(atom/over_object)
-	var/mob/M = loc
-	if(istype(M) && istype(over_object, /atom/movable/screen/inventory/hand))
-		var/atom/movable/screen/inventory/hand/H = over_object
-		M.putItemFromInventoryInHandIfPossible(src, H.held_index)
-
 /obj/item/watertank/attackby(obj/item/attacking_item, mob/user, list/modifiers, list/attack_modifiers)
 	if(attacking_item == noz)
 		remove_noz()