Improved performance of decimal arithmetics

[jorgecarleitao]

• Moved some operations to outside the hot loop.
• Removed some collects to Vec
• DRYed most of it.

[codecov]

Codecov Report

Merging #605 (41e98d4) into main (73ee16d) will increase coverage by 0.11%.
The diff coverage is 96.77%.

@@            Coverage Diff             @@
##             main     #605      +/-   ##
==========================================
+ Coverage   79.37%   79.49%   +0.11%     
==========================================
  Files         401      401              
  Lines       24966    24915      -51     
==========================================
- Hits        19817    19806      -11     
+ Misses       5149     5109      -40     

Impacted Files	Coverage Δ
src/compute/arithmetics/decimal/mod.rs	100.00% <ø> (ø)
src/compute/arithmetics/decimal/mul.rs	92.42% <93.02%> (+11.90%)	⬆️
src/compute/arithmetics/decimal/div.rs	92.30% <95.55%> (+11.53%)	⬆️
src/compute/arithmetics/decimal/add.rs	96.42% <100.00%> (+13.81%)	⬆️
src/compute/arithmetics/decimal/sub.rs	96.36% <100.00%> (+13.75%)	⬆️

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