Refactor stopifnot into cli_abort

[MichaelChirico]

Closes #2793

Implemented by Gemini with clean-ups by me.

[codecov]

Codecov Report

❌ Patch coverage is 96.87500% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.22%. Comparing base (a72dfbf) to head (0d148c5).

Files with missing lines	Patch %	Lines
R/undesirable_operator_linter.R	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2998      +/-   ##
==========================================
- Coverage   99.24%   99.22%   -0.02%     
==========================================
  Files         128      128              
  Lines        7265     7266       +1     
==========================================
  Hits         7210     7210              
- Misses         55       56       +1     

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[MichaelChirico]

some sort of software gore going on in the GitHub backend preventing me from applying all the suggested changes in a batch...