Exosuit Nuclear Power Cores (#18268)

* Added power cores, a type of large battery cell that get used by
exosuits. The nuclear and phoron variants are self-charging.
* Combat mechs now start with nuclear power cores, allowing them to
sustain themselves indefinitely, so long as they stay out of the action
for a bit.
* Removed basic power cells from the mechfab, replaced with the mech
powercores.
* Mech cell statuses now instantly update as soon as the cell charges or
discharges.
* Added a stack of 10 uranium to the machinist's workshop, which can
print two nuclear power cores.

code/game/objects/random/tech.dm

@@ -30,10 +30,12 @@
 	icon = 'icons/obj/random.dmi'
 	icon_state = "cell"
 	problist = list(
-		/obj/item/cell/crap = 10,
 		/obj/item/cell = 40,
 		/obj/item/cell/high = 40,
+		/obj/item/cell/crap = 10,
+		/obj/item/cell/mecha = 10,
 		/obj/item/cell/super = 9,
+		/obj/item/cell/mecha/nuclear = 5,
 		/obj/item/cell/hyper = 1
 	)