Switch packaging to hatch

[akx]

setup.py based packaging is legacy; using a PEP 517 build system is nicer and more modern, and hatch in particular is nice.

For one, the __version__ in miditoolkit/ and in the package metadata will no longer ever be out of sync, and you can also use hatch version patch (or minor or major) to conveniently bump it ✨

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7c8d7cc) 58.34% compared to head (e815fb5) 58.64%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #37      +/-   ##
==========================================
+ Coverage   58.34%   58.64%   +0.29%     
==========================================
  Files          12       11       -1     
  Lines         785      781       -4     
==========================================
  Hits          458      458              
+ Misses        327      323       -4     

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[Natooz]

I just learned about hatchling, I am all for it!
I just have a concern on its use in the test workflow, but I'm maybe missing something