Add http and restjson1 client protocols

[haydenbaker]

Description of changes:

• Adds the client protocol implementations
• Several TODOs, some not necessarily needed and some are blocked by other work (e.g. endpoint properties)
• Codegen will use the protocol when setting up the client request pipeline
  • for restjson, this could hypothetically look like:

class Weather:

    pipeline: RequestPipeline[HTTPRequest, HTTPResponse] = RequestPipeline(RestJsonClientProtocol(), ...)

    async def get_city(...) -> GetCityOutput:
        ...
        call = ClientCall(...)
        result = pipeline(call)
        ...
 

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[haydenbaker]

We already have validators to validate this kind of constraint model-side, but this would be good time to discuss whether we do any kind of validation in our trait definitions here. Thoughts?

[JordonPhillips]

It'll be under headers in the properties bag. Not necessary right now though.