feat(cluster): add k8s headless service for gossip peer discovery

Headless Service (clusterIP: None) with gossip-udp port 11204 for
DNS-based peer discovery in k8s deployments.

Signed-off-by: Sienna Meridian Satterwhite <sienna@sunbeam.pt>

infrastructure/base/ingress/pingora-headless.yaml

@@ -0,0 +1,16 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: pingora-headless
+  namespace: ingress
+  labels:
+    app: pingora
+spec:
+  clusterIP: None
+  selector:
+    app: pingora
+  ports:
+    - name: gossip-udp
+      port: 11204
+      targetPort: 11204
+      protocol: UDP