[Really Fucking Ready 4 Merge This Time] Fixes Comic's material datums being broken with stackable items

Created by: 9600bauds

It's honestly rather concerning just how unfinished and (presumably) completely untested everything Comic-related that I've touched so far has BEEN.

This makes it so that /obj/item/stack update their materials to account for the amount of items in stack. I did not make the Autolathe use recycle() because then it could smelt ore.

There is one bug I haven't been able to fix: Roundstart material stacks don't update their material count when the game starts. That means that, until you do something that updates the 50 rod stacks from Engineering (like take one rod out and put it back), they will still only give one rod's worth of metal if recycled. I tried a spawn() in /obj/item/stack's New(), but that didn't work. Listening to suggestions.

Fixes #7099 (closed)