Drop support for <3.8

[branchvincent]

Follow up to #438 (comment) along with CI simplification and an explicit dep on setuptools for 3.12

Closes #406

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.43%. Comparing base (6253fb8) to head (de4b5d1).

❗ Current head de4b5d1 differs from pull request most recent head bea565b. Consider uploading reports for the commit bea565b to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #440      +/-   ##
==========================================
- Coverage   89.44%   89.43%   -0.01%     
==========================================
  Files          34       34              
  Lines        2406     2405       -1     
==========================================
- Hits         2152     2151       -1     
  Misses        254      254              

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[Gallaecio]

Oh, I see this was the same as py.

Ideally we should have a min env with pinned minimum versions of dependencies, but since it was not there, I’m OK with removing it and adding it back properly later in a separate PR.