[EventCounters] Add example project

[mic-max]

Towards #215

Changes

Add simple project showing how to subscribe to event counters from specified event sources by name.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[codecov]

Codecov Report

Merging #860 (8a55a3d) into main (70f9f0f) will increase coverage by 0.00%.
The diff coverage is 80.00%.

❗ Current head 8a55a3d differs from pull request most recent head e71236c. Consider uploading reports for the commit e71236c to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #860   +/-   ##
=======================================
  Coverage   79.07%   79.07%           
=======================================
  Files         182      182           
  Lines        5614     5629   +15     
=======================================
+ Hits         4439     4451   +12     
- Misses       1175     1178    +3     

Impacted Files	Coverage Δ
...r.Stackdriver/Implementation/ActivityExtensions.cs	75.00% <ø> (ø)
...ons/Internal/ActivityEventAttachingLogProcessor.cs	93.33% <0.00%> (ø)
...on.EventCounters/MeterProviderBuilderExtensions.cs	100.00% <ø> (ø)
...elemetry.Instrumentation.Process/ProcessMetrics.cs	100.00% <ø> (ø)
...ensions.Docker/Resources/DockerResourceDetector.cs	82.60% <77.77%> (-1.27%)	⬇️
...ry.Extensions/Internal/DefaultLogStateConverter.cs	87.50% <100.00%> (ø)
...nsions/Logs/LogToActivityEventConversionOptions.cs	100.00% <100.00%> (ø)
...try.Extensions/Trace/AutoFlushActivityProcessor.cs	81.48% <100.00%> (ø)