Add `userdata` to tastudio greenzone states

[vadosnaprimer]

The userdata lua library currently only works with regular savestates but not tastudio greenzone (which uses memory savestates iirc?), which makes it problematic to restore lua values from past tastudio frames for things that can't be calculated on the fly for every given frame.

I have a counter that increments on a memory hook, and I need to store it in savestates in some way so I could go back without it infinitely incrementing on every advance and rewind, and I need to it also go back and show me values it had back then.

I think memory savestates altogether should include userdata whenever it's there (which is rare anyway, so shouldn't mess up anyone's workflow).

[YoshiRulz]

Are you able to use a custom column for the same purpose?

[vadosnaprimer]

As a theoretic workaround maybe, but it'd be too different from the intended workflow (custom columns are for things that change all the time and you need to see the dynamics), and doesn't make sense to just generally use one instead of the other.