BUG: long int formatting with thousands separator
The previous PR #52686 for issue #52272 had three flaws:

- it did not account for long integer display with thousands separator.
- it added tests that had nothing to do with the fix that it employed.
- a test added was specific only to the latex output.

This PR reverts the tests, and adds a more generic test which is applied to all styler output modes by default.

**The previous whatsnew for 2.1.0 is sufficient to leave in place**.

Thanks for the follow up @attack68 !