An example / proof of concept for stratified sampling in OpenTelemetry.NET

[kalyanaj]

This is an example / proof of concept for a basic stratified sampling in OpenTelemetry.NET.
Fixes #4207

Changes

Certain customers using OpenTelemetry want to do achieve stratified sampling. Stratified sampling is a way to divide a population (e.g., "all queries to a service") into mutually exclusive sub-populations aka "strata". For example, the strata here could be "all user-initiated queries", "all programmatic queries". Each stratum is then sampled using a probabilistic sampling method. This ensures that all sub-populations are represented.

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #4208 (9985aee) into main (1b1e4e5) will increase coverage by 1.44%.
The diff coverage is n/a.

❗ Current head 9985aee differs from pull request most recent head 5c5b2bc. Consider uploading reports for the commit 5c5b2bc to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4208      +/-   ##
==========================================
+ Coverage   83.27%   84.72%   +1.44%     
==========================================
  Files         296      295       -1     
  Lines       11685    11475     -210     
==========================================
- Hits         9731     9722       -9     
+ Misses       1954     1753     -201     

Impacted Files	Coverage Δ
...ZPages/Implementation/ZPagesExporterEventSource.cs	56.25% <0.00%> (-6.25%)	⬇️
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	96.87% <0.00%> (-0.79%)	⬇️
...Telemetry/Metrics/MetricPointOptionalComponents.cs	100.00% <0.00%> (ø)
...emetry/Metrics/Exemplar/SimpleExemplarReservoir.cs
src/OpenTelemetry/Metrics/AggregatorStore.cs	80.97% <0.00%> (+0.65%)	⬆️
src/OpenTelemetry/Metrics/MetricPoint.cs	64.94% <0.00%> (+22.15%)	⬆️

[cijothomas]

LGTM. Couple of nits, not blockers

[cijothomas]

@utpilla one more person proof reading would be good before merge.