Add stream conformance tests for HTTP/2, HTTP/3, and request streams

[stephentoub]

We've recently added a set of "conformance" tests for streams, a set of tests that we now run against many of the stream types in the core libraries. In #44204 we used these to test the response streams used for HTTP/1.1 with SocketsHttpHandler, but there are other streams it employs, including request streams for posts with HTTP/1.1 and then also a separate sets of types for HTTP/2 and again for HTTP/3. It'd be good to extend these tests to validate all of those.

cc: @geoffkizer

[ghost]

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[karelz]

Triage: Ideally we would have tests working for all versions, or at least have code coverage (based on the list in #44204) for all HTTP versions.