Improve performance of uv-python crate's manylinux submodule

[cthoyt]

Summary

This PR makes a few performance improvements:

1. Reduces the need to unpack and repack a _GLibCVersion tuple
2. Reduces the doubled call to _is_compatible(arch, glibc_version)
3. Moves the assignment of the tag variable directly into the yield, reducing memory allocation in case this is never used when _is_compatible(arch, glibc_version) is false
4. Combines the check of the glibc_version being in _LEGACY_MANYLINUX_MAP and the assignment to the variable together. I'm not sure if this is actually better, but using the assignment expression reduces this from 4 lines to 2

Test Plan

I upstreamed these changes in pypa/packaging#869. Otherwise, I'm pretty confident this is a minor change that works the same

[charliermarsh]

Thanks for this. I'm hesitant to make changes here since the code is vendored... Personally, I'd prefer to wait for this to merge upstream.

[cthoyt]

@charliermarsh totally agreed! I didn't realize it was vendored until after I had already made the PR... sorry for missing the README. I will watch out to see what the upstream group says, and ping you if we ever get some feedback!

Cheers

[charliermarsh]

Thank you!