id: Fix issues with group id handling described in #10006

[denendaden]

The uutils id previously exhibited different behavior from the GNU id, as shown in the following example:

$ sudo setpriv --reuid 3000 --egid 2000 --clear-groups target/release/id
uid=3000(u3000) gid=0(root) egid=2000(u2000) groups=0(root)
$ sudo setpriv --reuid 3000 --egid 2000 --clear-groups id
uid=3000(u3000) gid=0(root) egid=2000(u2000) groups=2000(u2000)

This discrepancy is because GNU id forms its list of groups by combining the effective group ID with a list of supplementary group IDs, whereas uutils id was, except when certain flags were provided, using the real group ID in place of the effective group ID. This pull request changes this behavior by passing None to get_groups_gnu, so that it uses the effective group ID instead of the group ID being passed to it, matching the GNU behavior.

Changes to numfmt were unrelated but necessary to get it to compile. I was not sure what to do about this.

Fixes #10006

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/shuf/shuf-reservoir (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/sort/sort-stale-thread-mem (fails in this run but passes in the 'main' branch)

[ChrisDryden]

Would it be possible to make an integration test for this issue to make sure we don't regress?

[ChrisDryden]

This code change of the numfmt linting should no longer be needed after rebasing

[sylvestre]

The id fix looks correct — using None to get the effective GID matches GNU.

However, the numfmt changes (replacing util_name() with uucore::util_name()) seem unrelated. Were these needed to fix a build issue? If so, they should probably be in a separate commit.

[sylvestre]

and needs to be rebased

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/unexpand/bounded-memory is now being skipped but was previously passing.
Congrats! The gnu test tests/seq/seq-epipe is now passing!