fix case of f(dict_array, dict_array) invocation

[davidhewitt]

Follow up to #63

Fixes a related case where invoking with two dictionary arrays would unpack the first array and then zip with the second incorrectly (before repacking as a dictionary), leading to a corrupted output.

Now instead we iterate the two arrays without unpacking the first, and then wrap as a new dictionary to keep the data type.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 68.57143% with 11 lines in your changes missing coverage. Please review.

Project coverage is 83.82%. Comparing base (38caf97) to head (add4038).

Files with missing lines	Patch %	Lines
src/common.rs	64.51%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #64      +/-   ##
==========================================
- Coverage   84.22%   83.82%   -0.40%     
==========================================
  Files          15       15              
  Lines        1014     1045      +31     
  Branches     1014     1045      +31     
==========================================
+ Hits          854      876      +22     
- Misses        111      120       +9     
  Partials       49       49              

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