993 progress: convert test_version.py & test_item.py to pytest

[teks]

Related Issue(s): #993

• Instead of trying to duplicate unittest.TestCase.maxDiff = None in pytest, I
  decided to just take it out and leave it to the user to use pytest -vv if
  they want.
• I mostly refrained from redesigning tests. My thinking is that the total Where reasonable, convert tests to free functions #993 changeset is
  already going to be enormous so don't make it worse by adding semantic density.
• unittest's TestCase.assertCountEqual() isn't conveniently available in
  pytest. I didn't try to duplicate the exact semantics since simpler assertions
  worked just as well, ie assert set(some_object) == {"a", "b"}
• Some classes are retained because they seem like a useful container to
  organize tests. The tests inside them were converted to pytest though.
• There's an http metadata entry in the revised cassette, X-Cache, that was a MISS in
  the original but is a HIT here. I assume that's harmless?
• I suggested I'd make "a few" PRs for Where reasonable, convert tests to free functions #993. I think I underestimated. 😞

PR Checklist:

• Pre-commit hooks and tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.47%. Comparing base (69e2cb0) to head (72b1f3c).
Report is 21 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1516   +/-   ##
=======================================
  Coverage   91.47%   91.47%           
=======================================
  Files          54       54           
  Lines        7542     7542           
  Branches      915      915           
=======================================
  Hits         6899     6899           
  Misses        457      457           
  Partials      186      186           

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[gadomski]

Thanks for the change, in general looks good! just one question.