Update HTTP client to have unique values for traceparent

[sayedihashimi]

We had a discussion with @jonsequitur and @davidfowl today regarding how the HTTP editor in VS uses the same value for the traceparent header. Each request sent in the HTTP editor should have its own unique value for traceparent. Jon is familiar with the issue and has a good idea about how to fix it.

[sayedihashimi]

@davidfowl I'm hearing from @samsp-msft that adding traceparent header is breaking some scenarios using OTel and he is recommending that we do not add that header. What's the correct behavior, do we need an option for this?

cc @vijayrkn

[shyamnamboodiripad]

The problem that Sayed mentions above has also been raised on this internal ticket - https://developercommunity.visualstudio.com/t/The-http-file-feature-is-sending-a-Trac/10791833

[jonsequitur]

@shyamnamboodiripad I don't think this is the same issue.