Add test to ParquetTestUtilsTest to check list projections and CaseMappers

[clairemcginty]

see #5885

couldn't reproduce this - I think in the original case, the AvroCompat import must not have been in scope. Adding the test to the suite since we hadn't actually covered that use case.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.54%. Comparing base (154b16c) to head (6bdcb0f).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5900   +/-   ##
=======================================
  Coverage   61.53%   61.54%           
=======================================
  Files         317      317           
  Lines       11653    11653           
  Branches      822      822           
=======================================
+ Hits         7171     7172    +1     
+ Misses       4482     4481    -1     

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