[RELEASE] Release opentelemetry-cpp 1.18.0

[marcalff]

Fixes #3145

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 ready!

Name	Link
🔨 Latest commit	7a7919a
🔍 Latest deploy log	https://app.netlify.com/sites/opentelemetry-cpp-api-docs/deploys/6744eea54bab8800087d5c54
😎 Deploy Preview	https://deploy-preview-3168--opentelemetry-cpp-api-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.84%. Comparing base (2a8c8bc) to head (7a7919a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3168      +/-   ##
==========================================
- Coverage   87.86%   87.84%   -0.01%     
==========================================
  Files         195      195              
  Lines        6151     6151              
==========================================
- Hits         5404     5403       -1     
- Misses        747      748       +1     

see 1 file with indirect coverage changes