[http-client-rust] Support File to represent file input and output in request/response body Implementation

[lmazuel]

[jhendrixMSFT]

We've been achieving this via bytes type with bytes encoding. I will say that using file is cleaner. What does it mean for bytes/bytes, are we going to deprecate that? Or do we end up with two ways to say the same thing? If so, which one do we recommend people use? Are there any subtle differences?

[heaths]

I don't like File, actually. It implies, well, a file. We're sending/receiving bytes or a stream, if you will. .NET doesn't use "file" either, but "stream". @lmazuel what is driving this requirement and why don't other languages do this?

As for streaming to/from files, we already have a pattern and document it. It doesn't require a separate type so I don't know how we'd inject "File" into the current workflow.