Add UUIDv6 and UUIDv7 draft versions

[oittaa]

https://github.com/uuid6/uuid6-ietf-draft/

A simple test case to show that these are actually sortable variants:

uuid6_1 = uuid6()
uuid7_1 = uuid7()
for _ in range(100000):
    uuid6_2 = uuid6()
    uuid7_2 = uuid7()
    assert uuid6_1 < uuid6_2
    assert uuid7_1 < uuid7_2
    uuid6_1, uuid7_1 = uuid6_2, uuid7_2

print(uuid6_1)
print(uuid7_1)

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[terryjreedy]

Discussion on the issue and linked thereon suggests that a) the draft standard has changed, making this PR outdated, and b) that approval of the newer draft seems to be getting closer. @oittaa , do you have any intention of updating this?

[encukou]

I'll close this for now. The standard is still a draft; the PR has conflicts and is based on an older version.
If anyone wants to work on this, please open an issue first:

• to separate the idea from the proposed implementation, and
• so that any fix-up PRs can be linked to the issue.

Once the new UUIDs become an official standard, I don't think the feature will need wider discussion than an issue.

[grillazz]

@encukou loooks it is now "proposed standard" > https://www.rfc-editor.org/rfc/rfc9562

[hugovk]

Which means we can now implement it:

https://en.wikipedia.org/wiki/Internet_Standard#Proposed_Standard

Let's continue in #102461 #89083.