message: orca: add qps to load reports.
  It's helpful to a client-side LB to know the total endpoint serving QPS when making LB decisions.
  This could also be used as a signal for Envoy's least loaded LB.
diff: @@ -22,10 +22,14 @@ message OrcaLoadReport {
  // during the request.
  double mem_utilization = 2 [(validate.rules).double.gte = 0, (validate.rules).double.lte = 1];
  + // Total RPS being served by an endpoint. This should cover all services that an endpoint is
  + // responsible for.
  + uint64 rps = 3;
  +
  // Application specific requests costs. Each value may be an absolute cost (e.g.
  // 3487 bytes of storage) or utilization associated with the request,
  // expressed as a fraction of total resources available. Utilization
  // metrics should be derived from a sample or measurement taken
  // during the request.
  - map<string, double> request_cost_or_utilization = 3;
  + map<string, double> request_cost_or_utilization = 4;
  }
  