Add labels to worker volumeClaimTemplate

[funkypenguin]

Why do we need this PR?

This PR adds support for applying labels to the PVCs created by the worker's statefulset, via volumeClaimTemplates. In some backup regimes, items are included / excluded from backups by virtue of their labels.

In my particular case, I don't want Velero to attempt to backup the workers' PVCs, so I need to add the velero.io/exclude-from-backup=true label to all the worker PVCs.

Changes proposed in this pull request

• Add a new chart value, persistence.worker.labels

Contributor Checklist

• [x] Variables are documented in the README.md
• [x] Which branch are you merging into?
  • master is for changes related to the current release of the concourse/concourse:latest image and should be good to publish immediately
  • dev is for changes related to the next release of Concourse (aka unpublished code on master in concourse/concourse)

Reviewer Checklist

This section is intended for the core maintainers only, to track review progress. Please do not fill out this section.

• [ ] Code reviewed
• [ ] Topgun tests run
• [ ] Back-port if needed
• [ ] Is the correct branch targeted? (master or dev)

[xtremerui]

Hi, master branch is updated could you rebase? Thank you!

[funkypenguin]

Hi, master branch is updated could you rebase? Thank you!

I think I've rebased correctly, but I'd appreciate a careful check! :)

[xtremerui]

you will also need to fix the DCO status check by signing off your commits.

EDIT: you will need to rebase master into your branch otherwise it will create a hugh commit history list like now.

[xtremerui]

Close due to #333