Require Jenkins 2.479.1 and Jakarta EE 9

[strangelookingnerd]

Require Jenkins 2.479.1 and Jakarta EE 9

Jenkins 2.479.1 provides Jakarta EE 9, Eclipse Jetty 12, Spring Security 6, and Java 17.

• Update plugin pom and baseline
• Use bytebuddy plugin
• Remove deprecations
• Use Java 17 language features

On a side note I highly recommend removing PULL_REQUEST_TEMPLATE.md, ISSUE_TEMPLATE.md and CODE_OF_CONDUCT.md from this repo and rely on the files provided by jenkinsci org.

Testing done

Confirmed that tests pass.

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 demonstrates feature works or fixes the issue

[strangelookingnerd]

@BorisYaoA Can this be merged?