increase test coverage of cairo-native-test

[tcoratger]

Increase test coverage of cairo-native-test:

• secp256r1 operations
• secp256k1 operations

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 97.23618% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 90.33%. Comparing base (dadd891) to head (7d43fd9).
Report is 2 commits behind head on main.

Files	Patch %	Lines
src/bin/cairo-native-test.rs	97.23%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #597      +/-   ##
==========================================
+ Coverage   89.13%   90.33%   +1.19%     
==========================================
  Files         109      109              
  Lines       34960    35306     +346     
==========================================
+ Hits        31161    31892     +731     
+ Misses       3799     3414     -385     

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