Fix some sheets of recycled material not having the correct starting materials
Created by: Zaers
So this issue was actually twofold: the first is byond being terrible at the initial() for lists and thus the starting_materials list was getting nulled when a sheet was sent to the pool and the second is that the stacking machines machines weren't correctly updating the materials in the sheets sent out
This fixes most parts of #13694 (I couldn't repro the not making plasteel part of it, so I can't specifically say if that's actually fixed)
- bugfix: Recyclers should now properly process sheets