Propagate distributed tracing context in HTTP tracing policy

[lmolkova]

Distributed tracing policy does not propagate context in HTTP headers

https://github.com/Azure/azure-sdk-for-go/blob/799c8579d2d8f32d3f30457cd6da736be08d9c6b/sdk/azcore/runtime/policy_http_trace.go

(which should be done according to our common policy)

DO pass the context to the backend service through the appropriate headers (traceparent and tracestate per W3C Trace-Context standard)) to support Azure Monitor. This is generally done with the HTTP pipeline.

This is used by greenfield Azure services to correlate things.

Some notes/examples on how it can be done

• OTel has implementation of W3C trace context propagator, here's the golang one
• We just need to call propagator.inject similarly to this example

Note: Otel gives user an ability to customize propagator, we should ignore one configured by the user and use W3C trace context implementation since that's the standard - Azure services are not going to support custom propagation formats.