[CI] replace cfssl with openssl for certificate generation

[7h3-3mp7y-m4n]

Fixes #3901

Changes

This PR replaces the usage of cfssl with openssl for generating certificates

• Replace cfssl certificate generation commands with openssl
• Update the generate_cert.sh script
• Update CI workflow to remove the cfssl dependency

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

[7h3-3mp7y-m4n]

This change might also require updates to the related documentation. Happy to add those if needed, would appreciate any feedback :)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.07%. Comparing base (3d35b54) to head (ed80b44).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3902   +/-   ##
=======================================
  Coverage   90.07%   90.07%           
=======================================
  Files         226      226           
  Lines        7217     7217           
=======================================
  Hits         6500     6500           
  Misses        717      717           

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[marcalff]

LGTM, thanks for the fix.