gh-128427: Add uuid.NIL and uuid.MAX

[ngnpope]

Adds constants for Nil and Max UUID formats as per RFC 9562.

• Issue: Support Nil and Max UUID formats from RFC 9562 #128427

---

📚 Documentation preview 📚: https://cpython-previews--128429.org.readthedocs.build/

[picnixz]

By the way, avoid force-pushing in the future as it makes reviews harder; we eventually squash commits and write our own commit message (force-pushing is accepted in some cases only but those are quite rare (like fixing up a really wrong commit that should not be seen at all, or changing the committer's email/name to due CLA reasons)).

[picnixz]

I forgot about the version and variant fields which I don't know what to do with.

[picnixz]

Just two nits and LGTM once a core dev allows it.

[hugovk]

Thanks, just a couple of docs suggestions.

[hugovk]

Linking directly to the section is helpful, perhaps we only need to mention the RFC number here? If so, we could update the same thing for uuid8 above.

Suggested change

	according to :rfc:`RFC 9562, §5.9 <9562#section-5.9>`.
	according to :rfc:`RFC 9562 <9562#section-5.9>`.

[hugovk]

Suggested change

	according to :rfc:`RFC 9562, §5.10 <9562#section-5.10>`.
	according to :rfc:`RFC 9562 <9562#section-5.10>`.

[encukou]

I think it works better with the section number in the text.

[hugovk]

Sure, let's merge.

@ngnpope, thank you your contribution!