chore: Transition to pyproject.toml and tox, support numpy 2, python 3.13

[effigies]

nitransforms currently claims incompatibility with numpy 2.0. Bringing testing into line with nibabel/nipreps, and will then begin pre-release tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.36%. Comparing base (e7757e2) to head (2d01dfd).
Report is 20 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #228      +/-   ##
==========================================
+ Coverage   94.65%   95.36%   +0.70%     
==========================================
  Files          15       28      +13     
  Lines        1758     2976    +1218     
  Branches      329        0     -329     
==========================================
+ Hits         1664     2838    +1174     
- Misses         77      138      +61     
+ Partials       17        0      -17     

Flag	Coverage Δ
unittests	95.06% <ø> (+0.41%)	⬆️

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[effigies]

Since there are no code changes, only CI, I'm going to merge this and release a version that doesn't hold back downstream packages. Please feel free to quibble about any of my choices and I will revert anything that I can't convince you is a good idea.