[Tests] Upgrade PHPUnit to 12

[smnandre]

• Bump phpunit/phpunit to ^12
• Update phpunit.dist.xml to the 12.5 schema

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (49b0a56) to head (e443435).
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Additional details and impacted files

@@             Coverage Diff             @@
##                main        #5   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity        52        52           
===========================================
  Files             13        13           
  Lines            273       273           
===========================================
  Hits             273       273           

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