Implement PEP 810

[pablogsal]

Linked PRs

• gh-142349: Implement PEP 810 #142351

[pablogsal]

The __future__ is now :)

[johnslavik]

CC @ZeroIntensity (mentorship): I'd give this a 3.15 too

[ZeroIntensity]

We usually don't add version labels for features, since they always imply the main branch (see the devguide). It's more controversial for bugs, such as in the case yesterday.