Add HPA autoscaling behavior field

[taylorshaulis]

Why do we need this PR?

This PR adds the behavior field to the worker HPA template. Once added the behavior field will allow users to adjust scale down and scale up windows beyond the default kubernetes settings.

https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/#default-behavior

Changes proposed in this pull request

• Add spec.behavior field to worker HPA to allow for custom scale behavior

Contributor Checklist

• [ ] Variables are documented in the README.md
• [ ] 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  • dev is for changes related to the next release of Concourse (aka unpublished code on master in concourse/concourse)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)

[taylorshaulis]

The sub settings for worker.autoscaling are not documented in the README.md. If that is necessary I can add documentation for the behavior field.

This is something new so hopefully we can just merge into the master branch without needing to back-port or wait for the next concourse release.