add validation for nans in y and number of classes > 10

[LeoGrin]

Change Description

Add validation for nans in y, and for number of classes > 10 for classification. This is already checked in the TabPFN local package, but right now be don't pass the error back to the client so the user doesn't see it + it's quite wasteful to send a request when this would fail anyway. In the future it would be good to share more of these function between the client and the local package but I think this is fine for now.
Contrary to the local package we use pd.isnull instead of check_array(force_finite=True) because the latter outputs a warning and behave less well with pd.NA or None values.

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Breaking changes

If you made any breaking changes, please update the version number.
Breaking changes are totally fine, we just need to make sure to keep the users informed and the server in sync.

Does this PR break the API? If so, what is the corresponding server commit?

Does this PR break the user interface? If so, why?

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[noahho]

Is this consistent with the client? Here, again we have some duplications and a shared interface could help?

[LeoGrin]

Mostly consistent, except for this part: "Contrary to the local package we use pd.isnull instead of check_array(force_finite=True) because the latter outputs a warning and behave less well with pd.NA or None values."
Agree once we refactor this should be in a shared package. We could also remove this once errors flow nicely from vertex.