Preserve client order of activity baggage items

[AndreyTretyak]

AddBaggage in reverse order to be the same as on the client

Addresses #26303

[Tratcher]

Test failure:
https://dev.azure.com/dnceng/public/_build/results?buildId=830373&view=ms.vss-test-web.build-test-results-tab&runId=26468712&resultId=105063&paneView=debug
Microsoft.AspNetCore.Hosting.Tests.HostingApplicationDiagnosticsTests.ActivityBaggagePreservesItemsOrder

Assert.Equal() Failure
Expected: KeyValuePair`2[] [[Key1, value1], [Key2, value2], [Key1, value3]]
Actual:   <<get_Baggage>g__Iterate|71_0>d [[Key1, value3], [Key2, value2], [Key1, value1]]

[AndreyTretyak]

Sorry, I forgot to mention.
There is a bug now in Activity for net5.0 rc1 dotnet/runtime#42659
After it would be fixed we would get the previous behavior of the Activity and UT should start working :)

[Tratcher]

@shirhatti @davidfowl @Pilchie is this a 5.0 candidate? It looks like the runtime PR was backported to 5.0.

[davidfowl]

This is broken in 3.x as well no?

[AndreyTretyak]

So HostingApplicationDiagnostics.cs behaivour was changing Activity.Baggage order in version 3.x, but in net5.0 preview version of the Activity there was a breaking change and in combination they worked properly. After Activity bug will be fixed it would be broken again (if we won't make the change).

[AndreyTretyak]

As far as I understand you are quite close to the 5.0 release, but in case if for some reason you're still considering including this fix I'll add some details why it's more important before net6.0.

Currently, the only way of changing Activity.Baggage is to call AddBaggage and if you call it twice for the same key it would look like the value was updated, but you're actually getting two values with the same key and after transfer GetBaggageItem will start returning the old value. So this case might be more common then it looks.

net6.0 could have an API for updating Baggage(dotnet/runtime#42706) and it might reduce the number of cases with the duplicated keys.

[Tratcher]

I don't see folks pushing to get this into 5.0 so it's been merged into master for 6.0.

[AndreyTretyak]

Okay, thanks, do I need to do something with the bug attached or it's up to you?

[shirhatti]

We should create a breaking change announcement for this behavior change