Description of problem:

When we create a CDI resource, the operator should expose the `kubevirt_cdi_cr_ready` metric, and create the `PrometheusRule` resource with the CDI alerts. Right now, if we create the CDI resource with a wrong infra node selector, the operator exposes the metric but the `PrometheusRule` is not created, and therefore alerts are not fired (namely `CDINotReady`)

See https://github.com/kubevirt/containerized-data-importer/blob/a19238ebbdadb8cc02ce91d3ed01c98935ff5475/tests/monitoring_test.go#L65 for the related test

Version-Release number of selected component (if applicable):

How reproducible: 100%

Steps to Reproduce:
1. Delete CDI if it exists
2. Create a new CDI with wrong .Spec.Infra.NodeSelector (p.e. "wrong": "wrong")

Actual results:

> kubectl get PrometheusRule -n cdi prometheus-cdi-rules
Error from server (NotFound): prometheusrules.monitoring.coreos.com "prometheus-cdi-rules" not found

Expected results:

> kubectl get PrometheusRule -n cdi prometheus-cdi-rules
NAME AGE
prometheus-cdi-rules 3m40s

Additional info: