Add a /status or /health for Retina 10093

[mereta]

Describe the bug
The readinessProbe currently uses localhost:10093/metrics to figure out if retina is ready. The metrics returned is dependent on scale, and can timeout if the data amount is high. Add a status/health path that returns fixed amount of data.

Hubble & legcay.

[rbtr]

since we already have ctrl runtime this is an easy way to add these: https://sigs.k8s.io/controller-runtime/pkg/healthz

[nddq]

@rbtr would the ctrl runtime's health and readiness reflect Retina's health and readiness as a whole? Since there could be other components that is not related to the controllers that are erroring out and ctrl runtime wouldn't know about

[rbtr]

it's modular, ctrlruntime healthz is a framework that we plug our own details in to