fix(metallb): Provide basic network policies

This patch should provide some basic network policies for the metallb
namespace helping to restrict access to services running inside.

infrastructure/metallb/kustomization.yaml

@@ -5,3 +5,7 @@ resources:
   - namespace.yaml
   - repository.yaml
   - release.yaml
+  - ../../shared/networkpolicies/allow-from-same-namespace.yaml
+  - ../../shared/networkpolicies/allow-from-monitoring.yaml
+patchesStrategicMerge:
+  - networkpolicy.yaml

infrastructure/metallb/networkpolicy.yaml

+---
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: allow-from-monitoring
+spec:
+  podSelector:
+    matchLabels:
+      app.kubernetes.io/instance: metallb
+      app.kubernetes.io/name: metallb