[SPARK-58015][INFRA][FOLLOWUP] Make dependency group names compliant with the PyPA specification

[ueshin]

What changes were proposed in this pull request?

This is a follow-up of #57093.

This PR renames internal dependency groups in pyproject.toml from names beginning with _ to names beginning with internal_. It also updates all corresponding include-group references.

No package requirements or dependency group contents are changed.

Why are the changes needed?

The PyPA Dependency Groups specification requires group names to be valid non-normalized names. Such names must begin and end with an ASCII letter or number, so the existing names beginning with _ are invalid.

• https://packaging.python.org/en/latest/specifications/dependency-groups/#the-dependency-groups-table

[dependency-groups] keys, sometimes also called “group names”, must be valid non-normalized names. Tools which handle Dependency Groups MUST normalize these names before comparisons.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

The existing tests should pass. All dependency group names and include-group references were validated, including checks for missing references and duplicate normalized names.

Also manually:

$ uv pip install --dry-run --group pyproject.toml:dev

Was this patch authored or co-authored using generative AI tooling?

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