feat(rust): Add DoubleEndedIterator for CatIter

[kgv]

Added a missing DoubleEndedIterator implementation for CatIter.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 81.11%. Comparing base (c34170f) to head (4814d0a).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...-core/src/chunked_array/logical/categorical/mod.rs	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21816      +/-   ##
==========================================
- Coverage   81.11%   81.11%   -0.01%     
==========================================
  Files        1613     1613              
  Lines      233270   233301      +31     
  Branches     2688     2691       +3     
==========================================
+ Hits       189227   189241      +14     
- Misses      43413    43430      +17     
  Partials      630      630              

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