chore: replace setuptools with hatchling, remove 'build' extra

[mwtoews]

This PR does the following:

• Changes the build backend from setuptools to hatch's hatchling. Why?
  • While both are PyPA projects, setuptools has some odd legacy concepts like MANIFEST.in and egg-info directories, that are not used with modern builds. It's an old system that is primarily maintained to maintain legacy behaviour and not to embrace modern enhancements.
  • Hatchling is a common and modern build backend, e.g. demonstrated as a default in guidelines. New features and plugins are actively developed for hatch and hatchling by Python core developers.
• Use the hatch-fancy-pypi-readme plug-in to stitch content for the documentation in PyPI. (There is more potential to this plug-in, such as amending changelog info from each release). See preview via uvx hatch project metadata readme.
• Remove the 'build' optional dependency (or extra), as this a prerequisite only for packaging builds, not an optional dependency. Builds can happen using several methods, e.g. python3 -m build or uv build or uvx hatch build etc.

I've done some comparisons of the sdist (.tar.gz) and bdist (.whl) outputs, and the contents are nearly identical.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.3%. Comparing base (bb9824e) to head (6e732c0).
Report is 52 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #2446     +/-   ##
=========================================
+ Coverage     68.4%   76.3%   +7.8%     
=========================================
  Files          294     293      -1     
  Lines        59390   60120    +730     
=========================================
+ Hits         40652   45886   +5234     
+ Misses       18738   14234   -4504     

see 250 files with indirect coverage changes

[wpbonelli]

The pypi fragments tool looks nice. Seems like we could improve on the current https://github.com/modflowpy/flopy/blob/develop/docs/PyPI_release.md.

[wpbonelli]

@mwtoews any ideas on this? I can reproduce it locally too. maybe pixi doesn't support hatchling yet?

[mwtoews]

It is because pixi.toml has --no-build-isolation --no-deps, which means that all build deps must be installed prior. Are these options needed? I think they could be removed; see MODFLOW-USGS/modflow6#2218

[wpbonelli]

@mwtoews any idea what the original motivation to use those options might have been?

Looks mostly OK without them. The extended build fails now but that seems like the 3rd party 7zip action doesn't play nice with something that is now in the pixi env.

[mwtoews]

Is this resolved with #2220? It's possible that removing --no-deps could have interfered the installed packages in some unexpected way. If the issue persists, then this pip install option can be re-instated.

[wpbonelli]

I think 2220 solves it.