Remove useless col_name_map arg from internal table functions

[taldcroft]

Description

The col_name_map argument passed around in the internal _join, _hstack and _vstack functions can be useful for diagnostics. However they are not exposed in the public API so they are not doing anything useful. I don't recall if things used to be different but at this point it seems they can just be cut.

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[mhvk]

Looks good. Agreed with @pllim that for changes in private functions a changelog entry is not needed (though if you really want it, I don't mind; but then it should be api, not feature)

[mhvk]

Somehow there is a merge conflict now...

[pllim]

Huh weird, there is conflict. You might need to rebase and also fix the pre-commit check.

[taldcroft]

Rebased and hopefully squared away now.

[pllim]

Looks like mhvk is happy. Diff also LGTM. Thanks!