all: Accept shortcuts for stringly-enum options

[BenWiederhake]

We already infer long arguments, like wc --tot being equivalent to wc --total. This PR introduces the same functionality for values, just like the GNU tools. In particular, this means the following calls are equivalent:

ls -l --time=a
ls -l --time=atime
ls -l --time=access

This example also demonstrates that alias resolution does not interfere with value inference: "a" is lexically ambiguous (it might mean "atime" or "access"), but has only one meaning (because "atime" and "access" are the same thing).

The implementation to do that was already there, but was only used in date(1) for some reason.

This PR is completely different from the following PRs:

• This PR changes how a value is parsed. Use time-style only if time is provided #6170 changes if a value is parsed at all.
• This PR adds a few additional values to the valid list. ls: compute the correct exit code #6173 changes the exit code of values that are just invalid ("banana"), if it is parsed at all.

[BenWiederhake]

(Whoops, sorry for the review request, that was too early.)

[BenWiederhake]

Changes since last push:

• Actually added the implementation for wc. Somehow I forgot to commit it, I'm a silly goose.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)

[BenWiederhake]

Changes since last push:

• Rebased to current main, to show that it still works

Is there anything else needed?

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/timeout/timeout is no longer failing!

[sylvestre]

LGTM but I would like @tertsdiepraam to comment as he often has great opinions on such subjects

[tertsdiepraam]

This is clever and I love it :)

[tertsdiepraam]

Excellent! Let's get this merged indeed!