Added Tempo Zipkin Egress Policy

relates to platform-one/big-bang/bigbang#1109

chart/templates/bigbang/networkpolicies/egress-tempo.yaml

+{{- if and .Values.networkPolicies.enabled }}
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: allow-tempo-egress
+  namespace: {{ .Release.Namespace }}
+spec:
+  podSelector: {}
+  policyTypes:
+  - Egress
+  # Allow access to zipkin
+  egress:
+  - to:
+    - namespaceSelector:
+        matchLabels:
+          app.kubernetes.io/name: tempo
+      podSelector:
+        matchLabels:
+          app.kubernetes.io/name: tempo
+    ports:
+    - port: 9411
+{{- end }}