[Instrumentation.SqlClient] Implements database metric db.client.operation.duration

[matt-hensley]

Fixes #
Design discussion issue #

Changes

Implements proposed db.client.operation.duration metric for SqlClient with required attributes.

Only implemented against .NET 6+ for now.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, 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

Attention: Patch coverage is 92.59259% with 6 lines in your changes missing coverage. Please review.

Project coverage is 89.02%. Comparing base (71655ce) to head (fdf77fe).
Report is 588 commits behind head on main.

Files with missing lines	Patch %	Lines
...ient/Implementation/SqlClientDiagnosticListener.cs	90.00%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2309       +/-   ##
===========================================
+ Coverage   73.91%   89.02%   +15.10%     
===========================================
  Files         267        9      -258     
  Lines        9615      410     -9205     
===========================================
- Hits         7107      365     -6742     
+ Misses       2508       45     -2463     

Flag	Coverage Δ
unittests-Instrumentation.SqlClient	89.02% <92.59%> (?)

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

Files with missing lines	Coverage Δ
...qlClient/Implementation/SqlActivitySourceHelper.cs	100.00% <100.00%> (ø)
...trumentation.SqlClient/SqlClientInstrumentation.cs	92.68% <100.00%> (ø)
...lClient/SqlClientMeterProviderBuilderExtensions.cs	100.00% <100.00%> (ø)
...ient/Implementation/SqlClientDiagnosticListener.cs	90.34% <90.00%> (ø)

... and 269 files with indirect coverage changes

[alanwest]

I merged this PR prematurely without a changelog. Spoke with @matt-hensley, he's working on making metrics work for .NET Framework in a follow on PR. Changelog will be updated there.