The deprecated metadata gets converted to a proper ItemStackMetaRef.
All keys stay the same except for:
- Cans that use `can_level` now, since they didn't store a serialized table in the metadata before.
- `charge` which is now `technic:charge`, since any item (also from other mods) may have a technic charge which can cause compatibility problems.
Backwards compatibility is kept but going back to older `technic` versions might result in misbehaving circuits.
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