Respect override for PipelineExecuting and PipelineExecuted

[peter-csala]

Pull Request

The issue or feature being addressed

• [Bug]: Customizing the severity of telemetry events has no effect: PipelineExecuted, PipelineExecuting #2750

Details on the issue fix or feature implementation

• Added code to respect SeverityProvider's overrides for PipelineExecuting and PipelineExecuted
• Added a bit of documentation
• Removed the explicit LogLevel check
• Added unit tests to cover the new code and the LogLevel checks

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2752   +/-   ##
=======================================
  Coverage        ?   96.15%           
=======================================
  Files           ?      309           
  Lines           ?     7123           
  Branches        ?     1005           
=======================================
  Hits            ?     6849           
  Misses          ?      221           
  Partials        ?       53           

Flag	Coverage Δ
linux	96.15% <100.00%> (?)
macos	96.15% <100.00%> (?)
windows	96.14% <100.00%> (?)

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[github-actions]

Thanks for your contribution @peter-csala - the changes from this pull request have been published as part of version 8.6.4 📦, which is now available from NuGet.org 🚀