FEAT(loki): configure storage and HA

- Rename extraVolume to avoid duplicate name
- Add emptyDir for /var/loki cache
- Migrate to shared storage with MinIO
- Configure HA with 2 replicas
- Revert to single replica for Single Binary mode

grafana/manifests/secret.yaml

@@ -20,3 +20,22 @@ spec:
       remoteRef:
         key: grafana
         property: ADMIN_PASSWORD
+---
+apiVersion: external-secrets.io/v1
+kind: ExternalSecret
+metadata:
+  name: grafana-db-password
+  namespace: grafana
+spec:
+  refreshInterval: 1h
+  secretStoreRef:
+    kind: ClusterSecretStore
+    name: vault-backend
+  target:
+    name: grafana-db-password
+    creationPolicy: Owner
+  data:
+    - secretKey: password
+      remoteRef:
+        key: postgresql
+        property: PASSWORD