ylib2to3 -- Fork lib2to3 with some blib2to3 backports; add structured pattern matching (match) and parenthesized-context-managers statement support (#1067)

Add ylib2to3, a copy of blib2to3.

- Yapf modifications to support match statement
- Disable double indent when splitting parameters after keyword
- Fix comment indent inside match
- Add vscode settings to gitignore
- Add testMatchStatementRemoveSpacesInCaseBracket
- Add credit to black
- Use post develop and install commands in setup.py
- Use metadata for yapf.__version__
- Install YAPF as it's own step in GitHub CI
- Remove PKG_INFO.ini, using importlib_metadata
- Move yapf.third_party to third_party, install at yapf_third_party though

This works, but you can't do a editable install with pip. You need to manually
add a line to site-packages/easy-install.pth for the fully qualified path to
<workspace>/third_party

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Co-authored-by: Charles <char101@ui.ac.id>
50 files changed