Expose pluginService GRPC API

Summary: We want to expose our plugin service GRPC API for external consumers. Currently, the only way to access the plugin API is through gql which our UI uses.

Test Plan: Skaffold build cloud

Reviewers: vihang

Reviewed By: vihang
Signed-off-by: Michelle Nguyen <michellenguyen@pixielabs.ai>

Differential Revision: https://phab.corp.pixielabs.ai/D11279

GitOrigin-RevId: 35ca4ab832414632e514b990b3bf0e969a8213b0

k8s/cloud/overlays/exposed_services_gclb/cloud_ingress.yaml

@@ -61,6 +61,13 @@ spec:
             name: cloud-proxy-service
             port:
               number: 5555
+      - path: /px.cloudapi.PluginService/
+        pathType: Prefix
+        backend:
+          service:
+            name: cloud-proxy-service
+            port:
+              number: 5555
       - path: /px.cloudapi.UserService/
         pathType: Prefix
         backend: