[POC] Better control of threads executed by opentelemetry-cpp

[marcalff]

Fixes #3174

Changes

Please provide a brief description of the changes here.

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

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[netlify]

✅ Deploy Preview for opentelemetry-cpp-api-docs canceled.

Name	Link
🔨 Latest commit	eedde5c
🔍 Latest deploy log	https://app.netlify.com/sites/opentelemetry-cpp-api-docs/deploys/6756addec3312500081a26ac

[codecov]

Codecov Report

Attention: Patch coverage is 54.71698% with 24 lines in your changes missing coverage. Please review.

Project coverage is 87.57%. Comparing base (762b73d) to head (eedde5c).

Files with missing lines	Patch %	Lines
...metrics/export/periodic_exporting_metric_reader.cc	54.55%	10 Missing ⚠️
sdk/src/logs/batch_log_record_processor.cc	47.06%	9 Missing ⚠️
sdk/src/trace/batch_span_processor.cc	64.29%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3175      +/-   ##
==========================================
- Coverage   87.83%   87.57%   -0.26%     
==========================================
  Files         195      196       +1     
  Lines        6154     6199      +45     
==========================================
+ Hits         5405     5428      +23     
- Misses        749      771      +22     

Files with missing lines	Coverage Δ
...pentelemetry/sdk/logs/batch_log_record_processor.h	100.00% <ø> (ø)
...ude/opentelemetry/sdk/trace/batch_span_processor.h	100.00% <ø> (ø)
...telemetry/sdk/trace/batch_span_processor_options.h	100.00% <ø> (ø)
sdk/src/trace/batch_span_processor.cc	91.22% <64.29%> (-2.90%)	⬇️
sdk/src/logs/batch_log_record_processor.cc	85.63% <47.06%> (-3.66%)	⬇️
...metrics/export/periodic_exporting_metric_reader.cc	76.43% <54.55%> (-5.30%)	⬇️