Enforce data rates between the proxy and destination

YARP should consider enforcing configurable minimum data rates when sending request body data to the destination and receiving response body data. AspNetCore servers have a similar feature for inbound and outbound data.

In the common case the request body will be fully uploaded before the response headers are received, so the request timeout will apply to that direction. The request timeout also includes the full processing time on the destination. There is currently no timeout for the response body after the response headers.

Timeouts don't scale well with large request and response bodies, data rates work better.

In the gRCP streaming and WebSocket scenarios you don't want any timeouts or fixed rates (?).