[BUG] Duplication between Azure.Core.Http spans and HTTP client ones

[lmolkova]

Library name and version

Azure.Core

Describe the bug

When OTel is configured to collect HTTP spans and Azure SDK spans, we report 2 spans for each HTTP call.

Azure SDK spans are 'better' because:

• we report additional information such as x-ms-*request-id values that are used by AzMon to correlate with server-side telemetry
• we can report precise duration including stream reading, retry number and other information generic instrumentation can't
• we work consistently on new and old .NET versions

So, we need to find a way to suppress native HTTP client spans.

The problem is not unique to Azure SDK, but there is no otel-wide story for it (open-telemetry/opentelemetry-specification#1767) and each language has its own way to suppress duplicates.

Here's the issue tracking it on OTel .NET side
open-telemetry/opentelemetry-dotnet#4641

Expected behavior

Only one span is created per HTTP call

Actual behavior

two spans are created per http call

Reproduction Steps

https://devblogs.microsoft.com/azure-sdk/introducing-experimental-opentelemetry-support-in-the-azure-sdk-for-net/ with latest otel

Environment

No response

[lmolkova]

A temporary alternative to open-telemetry/opentelemetry-dotnet#4641 could be using reflection to access OpenTelemetry.SuppressInstrumentationScope helper.

This would increase the number of AOT warnings, but none of the tracing things work with AOT anyway.

[lmolkova]

related: #35572, #29955