Add PEP751 lock files format support

[JonZeolla]

Add support for lockfiles PEP751 format (currently draft).

See the PEP discussions / review at python/peps#3870 and on the Python forums

s/o to @InSyncWithFoo for posting about this in discord

[charliermarsh]

Just to clarify, we shouldn't work on this unless the PEP is ultimately accepted.

[Dilski]

This PEP has full acceptance now 🥳

While I appreciate that this is hot off-the-press news, has there been any prior discussion on what/how UV will adopt this standard?

[Gankra]

now tracked in #12584