5010 redesign product form

Another one that's there for Deface, so it's easy to get at the particular fields.

I do find these dimension fields weird, as they're almost always left empty. I guess they're needed for some shipping methods, though, so they need to be present. It's a pain on the front end, because they take up most of the variant form with little value to most users. Still, that's another UX question for another day. I'm trying to keep focused on overall variant management for this PR.