Bump version

[gdalle]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Bump version to 3.12 for release

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.70%. Comparing base (17bb8a8) to head (452f4da).
Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #429      +/-   ##
==========================================
- Coverage   86.30%   85.70%   -0.60%     
==========================================
  Files          47       47              
  Lines        2913     2904       -9     
==========================================
- Hits         2514     2489      -25     
- Misses        399      415      +16     

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