Add Stream to Pipe Adapter

[jkotalik]

In 3.0, we will be starting to expose Pipes directly across the AspNetCore stack via PipeReader and PipeWriter. The initial design is to have new properties directly on the HttpContext to get HttpRequest.Body as a PipeReader and HttpResponse.Body as a PipeWriter.

One of the first needs we have is the ability to adapt a Stream into a Pipe. For example, when a middleware overwrites the Response.Body with a new stream, like ResponseCompression, Calling response.PipeWriter should return a PipeWriter that reflects the change made to the stream.

[Tratcher]

And a Pipe to Stream adapter...

[jkotalik]

#3971; probably don't want to implement both adapters in the same PR 😄

[jkotalik]

Majority of the work is done.