Refactor testing

[samsrabin]

Splits up gigantic test_relink.py into files with logical categorizations of tests.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.64539% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.39%. Comparing base (dd3603d) to head (3a432b8).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
tests/relink/test_find_and_replace_owned_files.py	99.09%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #11   +/-   ##
=======================================
  Coverage   99.38%   99.39%           
=======================================
  Files           3        9    +6     
  Lines         652      659    +7     
=======================================
+ Hits          648      655    +7     
  Misses          4        4           

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[jedwards4b]

Thanks for all your work on this.