chore(jenkins): Build with JDK17 and 21.

[gounthar]

Since #12 was merged, the builds are failing because the project is being built with JDK8, even though JDK11+ is mandatory. I suggest switching to JDK17/21, which should be compatible with this codebase and support future modernization.

Testing done

Unfortunately, the solution to this issue won't appear as successful checks because the Jenkins infrastructure uses the Jenkinsfile from the default branch to build this PR, not the one supplied. To use this Jenkinsfile, a maintainer needs to replay the failed build and provide the content of this Jenkinsfile to make it work.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed