prometheus: Enable live migration of rule configmaps to rule file crds

With this patch the Prometheus Operator checks if there are any
Kubernetes ConfigMaps inside the Prometheus namespace which fullfill the
`Spec.RuleSelector` requirement. If so, it creates a RuleFile for each
key in the `ConfigMap.Spec.Data` map inside the Prometheus namespace.

manifests/0prometheus-operator-0alertmanagerCustomResourceDefinition.yaml

@@ -11,7 +11,7 @@ spec:
   scope: Namespaced
   validation:
     openAPIV3Schema:
-      description: Describes an Alertmanager cluster.
+      description: Alertmanager describes an Alertmanager cluster.
       properties:
         apiVersion:
           description: 'APIVersion defines the versioned schema of this representation