feat(python): Allow bare .row() on a single-row DataFrame, equivalent to .item() on a single-element DataFrame

[alexander-beedie]

Closes #25143.

TLDR: as we already allow bare .item() calls on a (1,1) DataFrame, we should also allow bare .row() calls on a (1,n) DataFrame.

This ensures we have consistent/equivalent behaviour between the item() and row() methods, eg: allow the call without param values if there is only one possible valid option.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.77%. Comparing base (a3474bb) to head (916e156).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #25229   +/-   ##
=======================================
  Coverage   81.77%   81.77%           
=======================================
  Files        1713     1713           
  Lines      236780   236785    +5     
  Branches     3013     3015    +2     
=======================================
+ Hits       193629   193634    +5     
+ Misses      42381    42380    -1     
- Partials      770      771    +1     

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