Feature: Securely serve metrics using controller-runtime, instead of kube-rbac-proxy

[dlipovetsky]

Today, ASO securely serves metrics with kube-rbac-proxy. It can do this with controller-runtime itself, using a feature added in kubernetes-sigs/controller-runtime#2407, and available since the v0.16.0 release. This allows ASO to drop its dependency on kube-rbac-proxy.

For reference, the cluster-api core project motivated the above work, which it integrated in kubernetes-sigs/cluster-api#9264. Some years ago, cluster-api used to deploy kube-rbac-proxy, but removed it in kubernetes-sigs/cluster-api#4640.

Related slack conversation: https://kubernetes.slack.com/archives/C046DEVLAQM/p1706203810505779