feat: enable adding labels to prom-rules

[csatib02]

Fixes: #2129

Manually tested:

apiVersion: logging.banzaicloud.io/v1beta1
kind: Logging
metadata:
  name: all-to-file
spec:
  controlNamespace: logging
  fluentd:
    metrics:
      prometheusRules: true
      prometheusRulesLabels:
        kis: cica
        csulkos: pacal

kubectl get prometheusrule all-to-file-fluentd-metrics -o yaml | yq '.metadata.labels'
app.kubernetes.io/component: fluentd
app.kubernetes.io/managed-by: all-to-file
app.kubernetes.io/name: fluentd
csulkos: pacal
kis: cica