Improve inference for numeric columns

[mathemancer]

Related to #4370

This greatly improves the accuracy, safety, and performance of type inference for numeric columns.

Technical details

Previously, we simply tried to cast a sample of the column to numeric using our msar.cast_to_numeric(text) function. This regularly resulted in false negatives, and potentially resulted in false positives. Now, we:

• Test a (quite small) sample to try to find consistent group and decimal separators
• Try to cast the column to numeric, assuming that group and decimal separator for each row
• Return the group and decimal separator info, as well as the chosen type (numeric).

This PR does not make necessary changes to the front end code to enable all possible performance benefits of the back end changes. To get those benefits, the front end should submit the returned details.decimal_p and details.group_sep values back to the API to enable the faster casting behavior when actually confirming and saving the table.

TODO

In follow-up PRs, we should:

• Clean up column altering code a bit.
• Modify table previewing and column altering code to accept parameters for casting.

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the develop branch of the repository
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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[Anish9901]

LGTM!

[Anish9901]

I like this change, are you aware of a way to make only the failing tests verbose?

[mathemancer]

I asked the same question, but couldn't find a way.

[mathemancer]

@pavish I accepted your suggestion as per our call.

[pavish]

Looks good