Add support for .NET8.0 HttpClient metrics

[vishweshbankwar]

Towards open-telemetry/opentelemetry-dotnet-contrib#1753

Details: open-telemetry/opentelemetry-dotnet-contrib#1753
open-telemetry/opentelemetry-dotnet-contrib#1753

Changes

This PR adds support for metrics enablement that are part of .NET8.0. For HttpClient the following meters will be added to the MeterProviderBuilder when application targets .NET8.0 framework:

• Meter : System.Net.Http

  • http.client.request.duration
  • http.client.active_requests
  • http.client.open_connections
  • http.client.connection.duration
  • http.client.request.time_in_queue

• Meter : System.Net.NameResolution

  • dns.lookups.duration

Users may selectively opt-out with the help of views.

TODO: Update Readme

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 #4931 (f48e3e4) into main (38e21a9) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    open-telemetry/opentelemetry-dotnet#4931      +/-   ##
==========================================
+ Coverage   83.26%   83.29%   +0.02%     
==========================================
  Files         295      295              
  Lines       12375    12378       +3     
==========================================
+ Hits        10304    10310       +6     
+ Misses       2071     2068       -3     

Flag	Coverage Δ
unittests	83.29% <100.00%> (+0.02%)	⬆️

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

Files	Coverage Δ
...rumentation.Http/MeterProviderBuilderExtensions.cs	100.00% <100.00%> (ø)

... and 5 files with indirect coverage changes

[samsp-msft]

@JamesNK please review

[cijothomas]

Looks good.
Some comments from #4934 (review) are applicable here as well.

[CodeBlanch]

This is kind of interesting. How is it we don't report 2.0 now?

[vishweshbankwar]

@CodeBlanch See #4928

[CodeBlanch]

Some non-blocking feedback, LGTM