Support endpoint CPU load based load balancing

In current istio proxy, there is no endpoint cpu resource usage load based load balancing support but they are really needed specially in telecom environment. Now istio can only support subset, locality (zone,region) weight based load balancing, but it does not support cpu usage based load balancing.

can istio proxy support?

  1. get cpu usage from configured telemetry or internal mixer
  2. dynamically xDS to envoy with weight for different endpoint based on its cpu etc resource usage
  3. then envoy can distribute outgoing packet to different upstream according to its weight.