[BUG] Fix display for decimal types

[raunakab]

Overview

• fixed decimal printout
• was being printed out like {}.{}
• changed to Decimal(precision={}, scale={}) instead

[codspeed-hq]

CodSpeed Performance Report

Merging #2909 will not alter performance

_{Comparing bug/decimal-display (2907d77) with main (c66e384)}

Summary

✅ 17 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.29%. Comparing base (e3dd671) to head (2907d77).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2909      +/-   ##
==========================================
+ Coverage   74.36%   77.29%   +2.92%     
==========================================
  Files         596      596              
  Lines       72079    70930    -1149     
==========================================
+ Hits        53605    54822    +1217     
+ Misses      18474    16108    -2366     

Flag	Coverage Δ
	77.29% <ø> (+2.92%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/daft-schema/src/dtype.rs	81.03% <ø> (+7.99%)	⬆️

... and 65 files with indirect coverage changes