add SquashedFelt252Dict in executor

[tcoratger]

Should close #601.

Checklist

• Linked to Github Issue
• Unit tests added
• Integration tests added.
• This change requires new documentation.
  • Documentation has been added/updated.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.54545% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 91.41%. Comparing base (b09410b) to head (4f28173).

Files	Patch %	Lines
src/executor.rs	54.54%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #611      +/-   ##
==========================================
- Coverage   91.42%   91.41%   -0.01%     
==========================================
  Files         109      109              
  Lines       35881    35891      +10     
==========================================
+ Hits        32803    32811       +8     
- Misses       3078     3080       +2     

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[juanbono]

great PR! I'll take a look in a moment