Use proper public event loop group API

[bretambrose]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.62%. Comparing base (5d8d420) to head (cfd2b1e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #460      +/-   ##
==========================================
- Coverage   89.63%   89.62%   -0.02%     
==========================================
  Files          20       20              
  Lines        6137     6137              
==========================================
- Hits         5501     5500       -1     
- Misses        636      637       +1     

Files with missing lines	Coverage Δ
source/s3_client.c	90.09% <100.00%> (ø)

... and 1 file with indirect coverage changes