PeerAuthentication to enable STRICT mTLS

relates to https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/1018

chart/templates/bigbang/peerauthentication/enterprise.yaml

+{{- if and .Values.istio.enabled  .Values.gel.enabled }}
+apiVersion: "security.istio.io/v1beta1"
+kind: PeerAuthentication
+metadata:
+  name: loki-gel
+  namespace: {{ .Release.Namespace }}
+spec:
+  mtls:
+    mode: {{ .Values.istio.mtls.mode }}
+  selector:
+    matchLabels:
+      {{- include "enterprise-logs.selectorLabels" . | nindent 6 }}
+  {{- if and (eq .Values.istio.mtls.mode "STRICT") (.Capabilities.APIVersions.Has "monitoring.coreos.com/v1") }}
+  # Monitoring exception
+  portLevelMtls:
+    "3100":
+      mode: PERMISSIVE
+  {{- end }}
+{{- end }}