Fixes Freddy's bugged pizza (#94736)

## About The Pull Request

Fixes #93688 ?
There were a number of bugs collated into the above issue:

- An unidentified kind of pizza produced abstract slices when cut
- An abstract pizza was mapped into a ruin
- Robo pizza slices do not turn you into a robot

I could not replicate any of the existing pizza types spawning the wrong
slice type when cut, so I assume that bug A was caused by bug B and have
simply removed the abstract pizza from the ruin.
In addition I've removed the icon state from abstract pizza so it's more
obvious to mappers not to put it there, and to players that it's broken
(if you slice an abstract pizza it will use the mask to make them into
pizza slice shaped source errors which is kind of funny).

Finally the titular and more important change is that when you sliced a
pizza it was just creating a new pizzaslice object with 5 nutriment in
it, rather than a pizzaslice that inherited the reagents of the pizza it
was sliced from.
This meant that while margherita pizza has tomato juice in it,
margherita pizza slices did not and so on.
So now when we slice a pizza we distribute our pizza reagents into that
slice.
The upshot of this is that now when you slice a robo pizza, all the
slices will turn people into robots instead of none of them.

Melbert suggested making a unit test to ensure that all pizzas spawned
non-abstract slice types but that didn't actually seem to be a problem
so I didn't bother to do that yet.

## Why It's Good For The Game

Fixes bug.
Makes it harder to introduce bug by accident.

## Changelog

🆑
fix: Pizza slices now contain a proportional amount of whatever the
pizza contained, so sliced poisoned pizza will still be poisonous and
sliced robo pizza will still turn people into robots.
fix: Removed a bugged pizza from the pizza ruin and replaced it with a
margherita pizza.
fix: Bugged pizza no longer looks identical to functional margherita
pizza; it's a big error graphic.
/🆑

_maps/virtual_domains/fredingtonfastingbear.dmm

@@ -28,7 +28,7 @@
 /obj/effect/turf_decal/tile/blue/opposingcorners,
 /obj/effect/turf_decal/tile/blue/opposingcorners,
 /obj/structure/table,
-/obj/item/food/pizza{
+/obj/item/food/pizza/margherita{
 	pixel_y = 6
 	},
 /turf/open/floor/iron/kitchen,
@@ -226,7 +226,7 @@
 /obj/effect/turf_decal/tile/dark_red/opposingcorners,
 /obj/effect/turf_decal/tile/dark_red/opposingcorners,
 /obj/structure/table,
-/obj/item/food/pizza,
+/obj/item/food/pizza/margherita,
 /turf/open/floor/iron/kitchen,
 /area/virtual_domain)
 "mX" = (

code/game/objects/items/food/pizza.dm

@@ -1,11 +1,11 @@
 // Pizza (Whole)
 /obj/item/food/pizza
-	name = "pizza"
+	name = "bugged pizza"
+	desc = "This pizza should not be."
 	icon = 'icons/obj/food/pizza.dmi'
 	abstract_type = /obj/item/food/pizza
 	w_class = WEIGHT_CLASS_NORMAL
 	max_volume = 80
-	icon_state = "pizzamargherita"
 	food_reagents = list(
 		/datum/reagent/consumable/nutriment = 28,
 		/datum/reagent/consumable/nutriment/protein = 3,
@@ -103,6 +103,10 @@
 	slice.pixel_x += rand(-6, 6)
 	slice.pixel_y += rand(-6, 6)
 	user?.put_in_active_hand(slice)
+
+	slice.reagents.remove_all()
+	reagents.trans_to(slice, amount = reagents.total_volume / slices_left, no_react = TRUE)
+
 	slices_left--
 	if(slices_left <= 0)
 		qdel(src)
@@ -123,11 +127,11 @@
 
 // Pizza Slice
 /obj/item/food/pizzaslice
-	name = "pizza slice"
+	name = "bugged pizza slice"
+	desc = "This slice of pizza should not be"
 	icon = 'icons/obj/food/pizza.dmi'
 	abstract_type = /obj/item/food/pizzaslice
 	food_reagents = list(/datum/reagent/consumable/nutriment = 5)
-	icon_state = "pizzamargheritaslice"
 	foodtypes = GRAIN
 	w_class = WEIGHT_CLASS_SMALL
 	decomp_type = /obj/item/food/pizzaslice/moldy