Update legacy editables support for compatibility with setuptools >= 69

[sbidoul]

Since version 69, setuptools preserves _ in Name metadata and .egg-link files (before it converted them to -).

This is an attempt to make pip freeze and pip uninstall compatible with that behaviour, as well as fix various part of the testsuite that depended on that. The changes should be compatible with previous setuptools versions too.

This includes and extends #12458.

[notatallshaw]

Obvious question, but is there an easy way to run the Pip test suite using setuptools<69?

Some users pin their build dependencies either for their own project via pyproject.toml or for all their dependencies via PIP_CONSTRAINTS or using pip-tools.

[sbidoul]

You can test that by constraining setuptools in test/requirements.txt and tests/requirements-common_wheels.txt, and emptying the tests/data/common_wheels directory before running the nox test session.

[notatallshaw]

Thanks, I tested this branch locally using setuptools<69 on Linux Python 3.11 and all tests passed.

I did have one flaky test test_download_info_archive_cache_with_invalid_origin but that seems flaky on first run every time I changed my environment, regardless of what branch I was running it against.

[sbidoul]

Thanks for confirming @notatallshaw. I have not experienced the flakyness myself, though.