Initial networkPolicies for Promtail

Related to https://repo1.dso.mil/platform-one/big-bang/apps/sandbox/promtail/-/issues/5

BB MR: https://repo1.dso.mil/platform-one/big-bang/bigbang/-/merge_requests/1788

chart/templates/bigbang/networkpolicies/default-deny.yaml

+{{- if .Values.networkPolicies.enabled }}
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: default-deny-promtail
+  namespace: {{ .Release.Namespace }}
+spec:
+  podSelector:
+    matchLabels:
+      {{- include "promtail.selectorLabels" . | nindent 6 }}
+  policyTypes:
+  - Ingress
+  - Egress
+  ingress: []
+  egress: []
+{{- end }}