Switch to modern python packaging

[getzze]

Using setup.py and setup.cfg is deprecated in favor of a single pyproject.toml file:
https://setuptools.pypa.io/en/latest/userguide/pyproject_config.html

This PR removes these two files and the requirements*.txt files and puts all the relevant information in pyproject.toml.
Also the pingouin subfolder is removed, the tests are moved to the tests folder and the source to the src/pingouin folder.

The version number is uniquely defined in the __init__.py source file.

[raphaelvallat]

This is absolutely fantastic @getzze! Thank you for implementing this. I'll definitely re-use this as a template in some of my other projects. One request to update the datasets path and then we should be good to merge.

[raphaelvallat]

Approved! Thanks again, I'll run some final checks and merge later this week.

[raphaelvallat]

@getzze could you please rebase to the latest master, which includes a fix for the unit tests: #403? Thanks

[getzze]

I just rebased.

I saw that you don't run the tests on python 3.8 anymore, do you want me to bump the minimal python version in pyproject.toml also?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0fb0277) 98.54% compared to head (b30cced) 98.54%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #406   +/-   ##
=======================================
  Coverage   98.54%   98.54%           
=======================================
  Files          19       19           
  Lines        3359     3359           
  Branches      547      547           
=======================================
  Hits         3310     3310           
  Misses         26       26           
  Partials       23       23           

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[raphaelvallat]

Thank you!

I saw that you don't run the tests on python 3.8 anymore, do you want me to bump the minimal python version in pyproject.toml also?

I've disabled them because it led to a small rounding error for one particular unit test (logistic regression), most likely related to sklearn version differences. I didn't have time to investigate more, but all the other tests are working fine so I don't think there's a need to bump the minimal version to 3.8.

[hoechenberger]

Just FYI with this change, editable installations won't work the way you're used to. We experienced this issue with various MNE-Python-related projects.

The solution was to switch from the setuptools to the hatchling build backend. It's an easy thing to do and actually a more modern solution. I can help you do the switch either in this PR or in a followup.

See mne-tools/mne-python#12169 for details

[raphaelvallat]

@hoechenberger thank you for the heads-up! Very good to know. Let me merge this PR now and feel free to create a new one to use the hatchling backend.