Rework score token validation

[nanaya]

Combining hash and ruleset validation in the token model itself. build id stays as is because it's quite a bit more involved.

The way beatmap_hash is passed and validated is rather questionable 👀

[peppy]

Is this intended to ease the implementation of freestyle, or related to something else?

[nanaya]

it's related to the freestyle thing, yes

[notbakaneko]

I feel like there should be assertions some of the values don't change if the token already exists (because it doesn't make sense for them to change) but that's a different problem