Add option to publish not-ready addresses

[maxnitze]

What does this PR do?

Adds the option to set the publishNotReadyAddresses flag on the controller service. This allows traffic to get to the controller before its pod reports itself ready.

The Jenkins controller has its own way of dealing with requests while it is still starting. It shows a startup page until the service is ready. This also allows the "auto-refresh when done" feature when doing a restart from the UI to work (again).

Submitter checklist

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1. I bumped the "version" key in ./charts/jenkins/Chart.yaml.
2. I added a new changelog entry to ./charts/jenkins/CHANGELOG.md.
3. I followed the technical requirements.
4. I ran .github/helm-docs.sh from the project root.

Special notes for your reviewer

This flag was broken in very early Kubernetes releases (see kubernetes/kubernetes#58662 for example). So this feature is not working on Jenkns instances running in Kubernetes <=1.11. Which should be okay, I think 😄

[timja]

Hey LGTM. if you can rebase to fix the conflicts.

I do wonder whether this should be the default, but this is fine for now.

[maxnitze]

I do wonder whether this should be the default, but this is fine for now.

Yeah, thought so too. But I did not want to make this "breaking".

I rebased the branch onto main and solved the conflicts.