feat: Allow for parsing parquet file where the time zone is stored as lowercase "utc"

[MarcoGorelli]

closes #17547

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.50%. Comparing base (f7cac6b) to head (a77fb09).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17925      +/-   ##
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+ Coverage   80.48%   80.50%   +0.01%     
==========================================
  Files        1493     1493              
  Lines      196477   196477              
  Branches     2813     2813              
==========================================
+ Hits       158137   158164      +27     
+ Misses      37819    37792      -27     
  Partials      521      521              

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[sm-Fifteen]

Does the unit test fail if either the Some("UTC") or Some("utc") match is removed? I recall that Parquet does not actually store time zone specifiers, only UTC-normalized timestamps, and the weird timezone specifier in the Arrow dataframe was being added by Arrow2.

So where does this lowercase "utc" come from? If it does not come from the Parquet file, then this test case probably does not test for what you think it does.