k8s: update pod status logic to support native sidecars

[scarlettperry]

Description

A k8s sidecar is an init container that starts before the main app container and continues to run. This is unlike a regular init container which always runs to completion before the app container starts.

Reading

• https://github.com/kubernetes/enhancements/blob/master/keps/sig-node/753-sidecar-containers/README.md
• https://kubernetes.io/docs/concepts/workloads/pods/init-containers/
• https://github.com/kubernetes/kubernetes/blob/66e34012255abf1bbd0956a712817dad77c69c41/pkg/printers/internalversion/printers.go#L905-L908

PR changes
we need to account for the difference between an init sidecar container and a regular init container.

• to identify which is an init sidecar container, we check for where restart policy is not nil and set to restartalways
• to identify if the init sidecar is ready, we check that it has a running state and the container started is set to true. This is the same pattern as upstream kubectl get pods command.

Testing Performed

Existing unit tests
Manual