[Instrumentation.AspNetCore] Fix issue causing Activity is not exported when used with custom propagator/sampler.

[TimothyMothra]

Fixes #4626

When a custom propagator is used, the Instrumentation.AspNetCore library will create a new activity that is identified by a specific tag ("IsCreatedByInstrumentation").
For performance, only the first tag was inspected.

However, if a custom sampler is also used and adds tags that will affect the ordering and the instrumentation library will not identify the activity.
This causes activities to be dropped.

Changes

• Added new extension method ActivityHelperExtensions.TryGetTagValue()
• Fix HttpInListener to inspect all tags, not just first.

Merge requirement checklist

• CONTRIBUTING guidelines followed (nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Merging #4637 (5cae461) into main (66a6062) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4637      +/-   ##
==========================================
- Coverage   84.98%   84.96%   -0.03%     
==========================================
  Files         314      314              
  Lines       12683    12685       +2     
==========================================
- Hits        10779    10778       -1     
- Misses       1904     1907       +3     

Impacted Files	Coverage Δ
...tation.AspNetCore/Implementation/HttpInListener.cs	90.47% <100.00%> (+0.10%)	⬆️

... and 4 files with indirect coverage changes

[utpilla]

We don't have to add a new method. We could use the existing method GetTagValue: https://github.com/open-telemetry/opentelemetry-dotnet/pull/4637/files#diff-343f92e68a24f0d2d6ba9f91024a52f4f4b7085b5d30597dfec9303a07c14fc2R83

[TimothyMothra]

How strongly do you feel about using the existing method?

I think the TryGet is cleaner and saves an unnecessary assertion (if returnValue != null).

[reyang]

I think the min bar is:

1. don't duplicate code (e.g. if we want to add this method, at least the existing one GetTagValue should be updated so it'll leverage the TryGetTagValue).
2. keep it consistent - examine the existing usage and make proper update.

[utpilla]

saves an unnecessary assertion if (returnValue != null)

Even with the new method you have to check if (returnValue == true).

I would be in favor of reusing the existing method in this case and avoid having to introduce more code (and related tests) just to achieve a boolean check instead of a null check.

[reyang]

I would be in favor of reusing the existing method in this case and avoid having to introduce more code (and related tests) just to achieve a boolean check instead of a null check.

+1

[TimothyMothra]

removed