feat(http-add-on): replace kube-rbac-proxy with native secure metrics

[linkvt]

The kube-rbac-proxy sidecar is being discontinued and its images will become unavailable. This change uses controller-runtime's built-in metrics authentication instead, following kubebuilder recommendations, see kedacore/http-add-on#1369 .

Changes

• Remove kube-rbac-proxy sidecar container from operator deployment
• Add operator.metrics config (secure, auth, certDir) to values.yaml
  • The metrics endpoint defaults to being secure and requiring auth right now
  • We should IMO change the defaults later to match theones from the related PR to be insecure and without auth by default
  • Let me know if you're fine with changing the defaults now
• Replace proxy-role ClusterRole with system:auth-delegator binding
• Remove kube-rbac-proxy image and securityContext references

I tested accessing the metrics locally with the latest operator based on the main branch, worked well.

Checklist

• I have verified that my change is according to the deprecations & breaking changes policy
• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• README is updated with new configuration values (if applicable) learn more
• A PR is opened to update KEDA core (repo) (if applicable, ie. when deployment manifests are modified)

fyi @khauser , maybe you would like to test the chart

[khauser]

@linkvt : Very nice that you were integrating it 👍

Didn't we need also to release a new version of the addon and add it to the Chart.yaml und appVersion?

[linkvt]

Thanks!
Yes, updates to the Chart.yaml will happen when the release is triggered as far as I understand https://github.com/kedacore/charts/blob/main/CONTRIBUTING.md#shipping-a-new-version

We plan to release the next version probably next week.