Support BandwidthLimiting

[haorenfsa]

Description:

Describe the desired behavior, what scenario it enables and how it would be used.

We now only have request rate limiting. Can we also support bandwidth limiting? Is there any plan for this?

[optional Relevant Links:]

Any extra documentation required to understand the issue.

https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/other_features/bandwidth_limiting.html

[bjlhlin]

/assign