adding pod anti-affinity to Kyverno

[RinkiyaKeDad]

Anti-affinity allows us to constrain which nodes our pod is eligible to be scheduled based on labels on pods that are already running on the node rather than based on labels on nodes. We basically want multiple instances to be scheduled to different nodes.

1. Document how to do this manually.
2. Add it to the install.yaml (managed via Kustomize) and the Helm chart.

[chipzoller]

This won't be useful until Kyverno 1.4.0 releases and is added to the list of items in this discussion.