Add PrometheusRules globally on multiple user-defined namespaces.

Hi Team,

We have a customer requirement as follows.

As we know - 

• PrometheusRule shipped with Prometheus on ocp4 are restricted to "openshift-" and "kube-" ns
• Modifying them is neither possible nor supported
• Adding global Prometheus rule in openshift-monitoring is not supported
• Adding Prometheus rule in an application namespace restricts automatically the queries to the said namespace.

So in order to deploy the similar PrometheusRule customer has to apply the changes in each namespace.

For example.

Customers want to create the alert to check the restart of the pods in user-defined namespaces and the customer has multiple namespaces then it is leading to extra efforts because the customer has to deploy the same PrometheusRule in every namespace.