prototyping pythonfinder pep514 support

[matteius]

Prototyping bringing back a level of pep514 support to pythonfinder (would back-vendor it to pythonfinder if successful).

The checklist

• [ ] Associated issue
• [ ] A news fragment in the news/ directory to describe this fix with the extension .bugfix.rst, .feature.rst, .behavior.rst, .doc.rst. .vendor.rst. or .trivial.rst (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[matteius]

After spending a few hours on it tonight and trying to test it and seeing differences in behaviors between git bash and powershell, and also it finding my pyenv versions and maybe not even my windows versions -- I feel this still needs a ton of work. It seems nothing actually invoked the logic by default, and so I've spent a bunch more time trying on it, and have a bunch of local changes that don't work as well).

[matteius]

@TBBle -- I rewrote python finder over my lunch break -- it seems to work with pyenv on linux + windows store python installs from registry. https://github.com/pypa/pipenv/pull/6360 replaces this PR.