Fix bug related to Decimal negative value support

[mdrach]

This corrects a bug introduced in #679 , which resolves #676. The bug was caused by some confusion over endianness.

[codecov]

Codecov Report

Merging #684 (b5c4184) into main (fdb8c68) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #684      +/-   ##
==========================================
+ Coverage   69.76%   69.77%   +0.01%     
==========================================
  Files         303      303              
  Lines       16830    16830              
==========================================
+ Hits        11741    11743       +2     
+ Misses       5089     5087       -2     

Impacted Files	Coverage Δ
src/io/parquet/read/mod.rs	44.76% <100.00%> (ø)
src/compute/arithmetics/time.rs	26.60% <0.00%> (+0.91%)	⬆️
src/bitmap/utils/slice_iterator.rs	92.53% <0.00%> (+1.49%)	⬆️

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