Introduce Distributed Context API (distributed http context)

[tarekgh]

This issue tracking the work as the part of the issue #31372

Distributed context should support

• string/string (key-value pairs)
• Support scoping
• Not attached to Activity

[SergeyKanzhelev]

This change may include the following aspects:

1. Activity.Baggage can be re-wired to use this context API instead of associating context with Activity: https://github.com/dotnet/corefx/issues/30333
2. ASP.NET ILogger scopes can be sharing the same AsyncLocal for scopes tracking. This way ILogger logs may be correlated with the distributed scope more natively.

Scopes must be enclosed and allow inheritance of key/value pairs. So child scope have all parent scope key/value pairs available. As well as child scopes may completely re-start the scope with no values or remove (hide) certain keys from the parent scope.

[Aaronontheweb]

Why not just take a dependency on the OpenTracing or OpenTelemetry packages here?

[tarekgh]

@Aaronontheweb .NET Libraries trying to not taking dependency on OOB packages because this create a lot of problems related to package versioning and security fixes.

[danmoseley]

@tarekgh I found this one in https://themesof.net/?q=is:open%20kinds:teui as it was under a (closed) Epic. Do you believe it is properly part of the .NET 6 wave? I added it to the Cloud Native Epic instead so it is a sibling of your Metrics story, but I am not sure whether it is really part of .NET 6. If so we should remove its parenting or possibly close it.

[tarekgh]

@danmosemsft No this issue is not part of 6.0 planning and I am not aware of anyone need it urgently. I'll close it.

[danmoseley]

thanks!