[HttpClient] Fix activity displayName

[vishweshbankwar]

Fixes #
Design discussion issue #

Changes

updates http client activity display name as per specification https://github.com/open-telemetry/semantic-conventions/blob/main/docs/http/http-spans.md#name + some minor refactor

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 #5078 (3d339fa) into main (617ac6c) will decrease coverage by 0.33%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

❗ Current head 3d339fa differs from pull request most recent head bef12ad. Consider uploading reports for the commit bef12ad to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5078      +/-   ##
==========================================
- Coverage   83.36%   83.04%   -0.33%     
==========================================
  Files         296      296              
  Lines       12339    12335       -4     
==========================================
- Hits        10287    10244      -43     
- Misses       2052     2091      +39     

Flag	Coverage Δ
unittests	83.04% <100.00%> (-0.33%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...tp/Implementation/HttpHandlerDiagnosticListener.cs	72.18% <100.00%> (-0.62%)	⬇️
...plementation/HttpWebRequestActivitySource.netfx.cs	82.15% <100.00%> (-0.12%)	⬇️
src/Shared/RequestMethodHelper.cs	100.00% <100.00%> (ø)

... and 7 files with indirect coverage changes

[TimothyMothra]

LGTM. Just a nit for discussion:
Currently all the callers have to be knowledgeable of the spec to set the "HTTP" default value.

example:

activity.DisplayName = RequestMethodHelper.KnownMethods.TryGetValue(request.Method.Method, out var httpMethod) ? httpMethod : "HTTP";

Would it make sense to have a helper method that fully encapsulates this default value with a reference to the applicable spec?

activity.DisplayName = RequestMethodHelper.GetDisplayName(request.Method.Method);

[vishweshbankwar]

LGTM. Just a nit for discussion: Currently all the callers have to be knowledgeable of the spec to set the "HTTP" default value.

example:

activity.DisplayName = RequestMethodHelper.KnownMethods.TryGetValue(request.Method.Method, out var httpMethod) ? httpMethod : "HTTP";

Would it make sense to have a helper method that fully encapsulates this default value with a reference to the applicable spec?

activity.DisplayName = RequestMethodHelper.GetDisplayName(request.Method.Method);

Done!