Request-Response Streaming Operation

[xiazhvera]

Issue #, if available:

Description of changes:
The pr depends on bug fixes of awslabs/aws-c-io#725 to make sure the streaming operation would terminated properly while the client is shutdown.

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[sbSteveK]

Trivial: Should we allow this to be nil by making it optional ( [UserProperty]? ) ? Other optional properties are treated as optional so it feels a little off for this "Optional" to not be.

[xiazhvera]

I see the concern here. However, since Swift requires explicit validation before using optional values, using an empty array to represent "optional user properties" would simplify the code by avoiding the nil checks/unwrap.

[sfod]

Trivial: "Submits a generic request to the request-response client" -> "Initiates a request-response operation"

[bretambrose]

Please no "ResponseResponse". If I did it in the C API it was a mistake there too, but let's not propagate it.

[sbSteveK]

This feels misleading because it's labeled here and elsewhere as "JsonPath" but it's actually just the unique string used to correlate. Unsure what we should do from a naming the member perspective but I don't think we should say it's a "JSON path" in the description we provide.

[xiazhvera]

Calling it a "path" still feels accurate to me. Currently, the correlation token is just a top-level string, so the "path" is simply "clientToken" like in this example:

Response{
  "clientToken": "<token>"
}

But our current design leaves room for future responses where the token could be nested. For example, in the following case, the path might be something like "level1.level2.clientToken".

Response{
  "level1": {
    "level2" : {
        "clientToken": "<token>"
    }
  }
}

[sbSteveK]

Same as above

[sbSteveK]

Review trivial suggestions then ship