Envoy Gateway: xDS Control Plane Information Disclosure when operating in GatewayNamespaceMode

Impact When Envoy Gateway runs in GatewayNamespaceMode provider.kubernetes.deploy.type=GatewayNamespace, the xDS gRPC server is configured with a StreamInterceptor for JWT authentication but no UnaryInterceptor. The go-control-plane xDS server exposes both streaming and unary Fetch RPC methods fo...