HttpTelemetry instrumentation for HTTP/3

[MihaZupan]

Newly added System.Net.Http Telemetry should be expanded to HTTP/3 in the future.

Currently, only the Start/Failed/Stop events are available for HTTP/3.

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[MihaZupan]

@ManickaP @CarnaViire Are there any major code changes planned for HTTP/3 during 7.0 that would be complicated if telemetry code were in place already?
I'm happy to do the change as long as it doesn't cause you more work in the long run.

[ManickaP]

No major changes planned. There might be some perf work around stream data handling, like: #58445.
I don't think adding telemetry now will cause more work for us in the future. Feel free to tackle this and thanks for taking the initiative here!