Drop CI build matrix & testing on macOS images

[atifaziz]

This PR removes building & testing on macOS from CI pipelines.

The macOS machines on CI platforms seems to fail often, adds to the overall CI checks times and brings little benefit. It was historically interesting for testing against Mono on macOS and validating compatibility of tools/binaries used in Bash scripts.

This can always be revived if needed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.23%. Comparing base (088df95) to head (ede868e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1078   +/-   ##
=======================================
  Coverage   93.23%   93.23%           
=======================================
  Files         112      112           
  Lines        3400     3400           
  Branches      962      962           
=======================================
  Hits         3170     3170           
  Misses        214      214           
  Partials       16       16           

Flag	Coverage Δ
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