Investigate permanent errors in the object reconcilers

[adrianludwin]

I believe that object reconcilers can get into a bad state, e.g. if their CRDs are deleted, which can only be resolved by restarting HNC. These bad states don't necessarily affect anything but can pollute the logs. In addition, the OnChangeNamespace function in #180 introduces a goroutine that has no ability to return errors, so we don't have a great story to handle anything that permanently breaks a reconciler.

We should look holistically into how a reconciler can be broken, and how HNC can fix it.

[adrianludwin]

Suggestion from @rjbez17:

Alternatively, we could just update the healthz endpoint in this case to tell the control plane we aren't healthy. We could then loop forever in the code and lets k8s restart us based on liveness probes. If the loop recovers we could update the endpoint to be healthy again. It would also give a better 'audit trail' of HNC health for monitoring tools as it'll show as unhealthy in k8s instead of random restarts.

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/lifecycle rotten

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/close

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@k8s-triage-robot: Closing this issue.

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/close

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