Switch build testing to Java 21

[denis-yuen]

Description
Switch testing to Java 21. Will probably switch jar later as we gain experience
Unblocked with https://github.com/dockstore/dockstore-deploy/pull/794

Review Instructions
Builds succeed. Support programs like topic sentence generation, submission, metrics, etc. should just work. Could login to the deployer and run them, display help, etc.

Issue
https://ucsc-cgl.atlassian.net/browse/SEAB-6611

Security
If there are any concerns that require extra attention from the security team, highlight them here.

Please make sure that you've checked the following before submitting your pull request. Thanks!

• Check that you pass the basic style checks and unit tests by running mvn clean install in the project that you have modified (until https://ucsc-cgl.atlassian.net/browse/SEAB-5300 adds multi-module support properly)
• Ensure that the PR targets the correct branch. Check the milestone or fix version of the ticket.
• If you are changing dependencies, check with dependabot to ensure you are not introducing new high/critical vulnerabilities
• If this PR is for a user-facing feature, create and link a documentation ticket for this feature (usually in the same milestone as the linked issue). Style points if you create a documentation PR directly and link that instead.

[denis-yuen]

Hmmm, need equivalent of https://github.com/dockstore/dockstore/pull/5297/files to pull out all the system rules

Found simpler, if uglier solution

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.13%. Comparing base (da37df9) to head (60c8f7e).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #499   +/-   ##
==========================================
  Coverage      45.13%   45.13%           
- Complexity       305      306    +1     
==========================================
  Files             47       47           
  Lines           2663     2663           
  Branches         205      205           
==========================================
  Hits            1202     1202           
  Misses          1368     1368           
  Partials          93       93           

Flag	Coverage Δ
metricsaggregator	36.91% <ø> (ø)
toolbackup	23.16% <ø> (ø)
tooltester	17.31% <ø> (ø)
topicgenerator	19.67% <ø> (ø)

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