migrate setuptools pep621 config to pyproject.toml

[jenshnielsen]

This moves the supported and non experimental
parts of setuptools config to pyproject.toml
These are the parts standardized by pep621 and
supported in setuptools >=65

These are the supported parts of #4049

• Verify how this works with older versions of pip and make sure we handle that reasonably
• Check that editable/normal install from source works as expected
• Verify that package content is identical
• requirements-builder does not yet support this so out min requirements build fails: Pr open here feat: add support PEP621 compatible pyproject.toml inveniosoftware/requirements-builder#56

[codecov]

Codecov Report

Merging #4382 (a776df5) into master (ad35f92) will decrease coverage by 0.94%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4382      +/-   ##
==========================================
- Coverage   68.35%   67.41%   -0.95%     
==========================================
  Files         275      275              
  Lines       31021    31021              
==========================================
- Hits        21205    20912     -293     
- Misses       9816    10109     +293     

[jenshnielsen]

@astafan8 I think this is ready for review if we are ok to use my fork of requirements-buider until support is merged upstream

[astafan8]

let's go for it! on the flaming edge of the python tech :)