Support W3C Propagator

[tarekgh]

Contribute to #103174

• Introducing the W3C Propagator conforming to the W3C specs of the trace context and Baggage.
• Changing the default propagator to W3C Propagator. i.e. DistributedContextPropagator.Current and DistributedContextPropagator.CreateDefaultPropagator() now will have the W3C Propagator as the default propagator.
• Created the issue to track exposing DistributedContextPropagator.CreateLegacyPropagator() to allow user to opt-in to the legacy propagator.
• A breaking change [Breaking change]: Switch the default trace context propagator from Legacy to W3C docs#45793 is filled.

[Copilot]

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[dotnet-policy-service]

Added needs-breaking-change-doc-created label because this PR has the breaking-change label.

When you commit this breaking change:

1. Create and link to this PR and the issue a matching issue in the dotnet/docs repo using the breaking change documentation template, then remove this needs-breaking-change-doc-created label.
2. Ask a committer to mail the .NET Breaking Change Notification DL.

Tagging @dotnet/compat for awareness of the breaking change.

[tarekgh]

@noahfalk@CodeBlanch@rajkumar-rangaraj@lmolkova@samsp-msft

[tarekgh]

@MihaZupan@antonfirsov we are changing the default propagator to use the new W3C one instead of the legacy one. Looks like many http/socket tests are failing because of that. Could you please help by looking at the failed tests and fix these?

The new W3C propagator is not supporting Request-Id anymore and only supports traceparent header. Legacy activities created with hierarchical id formats will not be propagated using the new W3C propagator. Additionally, the new W3C is more restricted to the W3C specification so most likely tests can be using some test values which are not compliant with the specs.

If want to continue testing hierarchical activity ids, you can consider reset the current propagator to the legacy one. We haven't exposed API to return that yet, but the test can use reflection if want to. Let me know and I can help.

[tarekgh]

CC @JamesNK for awareness.

[noahfalk]

A couple suggestions inline but other than that LGTM!

[JamesNK]

Does ASP.NET Core need to do anything to read headers added to requests? Or does it already work?

[tarekgh]

Does ASP.NET Core need to do anything to read headers added to requests? Or does it already work?

aspnet core support both header names baggage and Correlation-Context, so I expect will still continue without a problem. We need to watch if we run into any issue though.