Refresh for JDK21

[CodeSmell]

Updated the JDK and major dependencies
See UPGRADE_SUMMARY.md for details

Related to Issue #158

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.30%. Comparing base (169bd88) to head (f47cc1f).
⚠️ Report is 3 commits behind head on master.
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Additional details and impacted files

@@             Coverage Diff              @@
##             master     #159      +/-   ##
============================================
- Coverage     86.37%   86.30%   -0.07%     
- Complexity      954      957       +3     
============================================
  Files            84       84              
  Lines          2568     2578      +10     
  Branches        246      246              
============================================
+ Hits           2218     2225       +7     
- Misses          235      237       +2     
- Partials        115      116       +1     

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