fix(cubesql): Enable constant folding for unary minus exprs

[MazterQyou]

Check List

• Tests has been run in packages where changes made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Description of Changes Made

This PR enables constant folding for unary minus expressions (-expr), fixing a regression introduced with d5a935a. Related test is included.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1938053) 47.95% compared to head (4e5dba3) 72.86%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #7707       +/-   ##
===========================================
+ Coverage   47.95%   72.86%   +24.90%     
===========================================
  Files         154      335      +181     
  Lines       20914    56895    +35981     
  Branches     5377     5377               
===========================================
+ Hits        10030    41455    +31425     
- Misses      10143    14699     +4556     
  Partials      741      741               

Flag	Coverage Δ
cube-backend	47.98% <ø> (+0.02%)	⬆️
cubesql	87.32% <100.00%> (?)

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