Update Gradle to 8.6 and add wrapper validation

[leonard84]

This PR update Gradle to 8.6 including updated to the generated scripts.
It also adds the gradle/wrapper-validation-action action to validate the embedded gradle-wrapper.jar.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.25%. Comparing base (5e206e1) to head (a70fe51).

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #333   +/-   ##
=========================================
  Coverage     91.25%   91.25%           
  Complexity     1213     1213           
=========================================
  Files            76       76           
  Lines          3157     3157           
  Branches        490      490           
=========================================
  Hits           2881     2881           
  Misses          164      164           
  Partials        112      112           

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[casid]

Thank you for the upgrade!