[Kubernetes/Workloads] Replica Available monitor needs his own separate replica_group_by variable

[francovp]

When using, for example, the following replica_group_by values ["kube_namespace", "kube_replica_set", "kube_cluster_name"] the replica_available monitor doesn't get groups metrics because the kube_replica_set doesn't exists in the kubernetes_state.deployment metric used by that monitor.