Upgrade the vendored `packaging` to 22.0+

[pradyunsg]

Filing an issue to track this since there's a lot of pieces involved as far as I can tell.

xref pypa/packaging#530

Needs:

• A concensus on the deprecation plan for legacy versions / requirements + rollout
• Remove reliance on LegacyVersion setuptools#2822 or some alternative

Blocks:

• Improving error messages around bad requirements being provided to pip; notably Improve Requirement/Marker parser with context-sensitive tokenisation packaging#624
• Improving startup times (by removing pyparsing's parser initialization at import time from `packaging.requirement)
• PEP 685 (Adhere to PEP 685 when evaluating markers with extras packaging#545)
• Better handling of "old" MacOS tags
• Reverting Cache Requirement Object Creation #10550, since the parser is over 95% faster and uses less memory now.

[pradyunsg]

A concensus on the deprecation plan for legacy versions / requirements + rollout

For this, my thought process is that we do this in the span of a 3 month deprecation before removal; where pip would warn on every Requirement / Version that we create -- a deprecation warning about the LegacyVersion/LegacySpecifier being used and the source string that triggers it.

One behaviour that I'm flip-flopping on: Should we skip wheels / sdists that contain requirements with this value in the dependency resolver, or should we reject them with an error?

[nanonyme]

My two cents is if they are the best version that can be resolved, error makes sense. If best version is something else, ignore. Does that make the best version resolution too slow?

[timfel]

Just a note, since https://github.com/pypa/packaging/pull/607/files was merged and wheel and meson-python have updated to include those changes, locally built packages can no longer be installed on GraalPy unless we downgrade wheel and meson-python. The linked PR changed the abi tag for GraalPy. Just leaving this note here to say I wouldn't mind if pip updated it's vendored packaging at some point :)

[sbidoul]

I was (briefly) looking at deprecating LegacyVersion and LegacySpecifier.

Doing it in pip sounds non trivial. One thing that may be easier is to surface the two deprecation warnings that are already present in our vendored copy of packaging. The downside of that is that the warning messages would possibly lack context.

One hurdle I face, though, is actually finding examples of usages of these that actually work with pip main. If anyone can provide some that would be helpful.