[RELEASE] Release opentelemetry-cpp 1.29.0

[marcalff]

Fixes #4410

Changes

Please provide a brief description of the changes here.

• Release opentelemetry-cpp 1.29.0

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.41%. Comparing base (e81d957) to head (83a7804).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4560   +/-   ##
=======================================
  Coverage   86.41%   86.41%           
=======================================
  Files         524      524           
  Lines       20435    20435           
=======================================
  Hits        17657    17657           
  Misses       2778     2778           

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[ThomsonTan]

Thanks for making the new release.