Make kube-node-ready optional

[mikkeloscar]

kube-node-ready has lost its usefulness for several reasons:

• Karpenter nodes don't run it which is the majority of nodes in most clusters
• kube-node-ready was introduced at a time where we had a problem that ASGs could be automatically AZ reblanced, terminating nodes before the replacements had a chance to startup. Having nodes only marked ready in the ASG once the kube-node-ready pod was running slowed this rebalancing down. We no longer have AZ rebalance enabled, so not relevant.
• We used it as a pseudo way to check pod network functionality, but we now have kubenurse which does a better job at this.

This PR introduces a config-item kube_node_ready_enabled which lets us disable it. The intention is to first disable in test clusters and later in all clusters.

This is indirectly motivated by switching to IMDSv2 for which kube-node-ready is not compatible with.

[mikkeloscar]

👍

[demonCoder95]

👍