chgrp: use map instead of match in parse_gid_and_uid()

[Devel08]

No description provided.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/retry (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/tail-n0f is now passing!

[xtqqczze]

Instead of formatting the error inline, we could follow the pattern used by other utils and introduce the thiserror crate.

That would let us move the error definitions into an enum, e.g.:

#[derive(Error, Debug)]
enum ChgrpError {
    #[error("{}", translate!("chgrp-error-invalid-user", "from_group" => .from_group))]
    InvalidUser { from_group: String },
}

[xtqqczze]

The default implementation will already use an exit code of 1:

impl UError for ChgrpError {}

[xtqqczze]

nit: can this go between clap and uucore?

At some point I want to alphabetise these sections and that will minimise the diff.

[Devel08]

alr

[xtqqczze]

LGTM