Add TransferRate response extension to throttle the response stream for any response

[skwasjer]

Currently the RateLimitedStream can be used to throttle the transfer rate of a stream based response, but it requires another stream (to wrap). It would be ideal to have a ResponseBuilder extension that makes it possible to throttle any type of response content, be it string content, byte array, json, xml, etc. This makes it really useful to test client implementations that operate on generally slow connections, IOT/wireless devices, etc.

The behavior should not be mutually exclusive with Latency but instead - if configured together - work together. The behaviors should always run in the correct order (and before any other unrelated behavior), regardless of how the user configures it through the fluent API.

Something like:

mockHttp
    .When(...)
    .Respond(with => with
        .Body(...)
        .Latency(TwoG)
        .TransferRate(TwoG)
    );

Where the behavior pipeline should become:

• latency > transfer rate > status code > body > etc.