docs: Enhance Edwards Curve Documentation and Test Readability

[DeVikingMark]

Motivation

The Edwards curve implementation in the codebase, while functionally sound, had areas where documentation could be enhanced to improve developer experience. Clear and comprehensive documentation is crucial for maintaining code quality and helping new contributors understand the codebase better.

Specifically, the EdwardsParameters trait and its associated methods lacked detailed documentation, making it potentially challenging for new developers to understand the purpose and usage of these important components.

Additionally, the test module used single-letter type aliases, which, while functional, didn't follow Rust's best practices for code readability.

Solution

This PR implements two main improvements:

1. Added comprehensive documentation to the EdwardsParameters trait and its methods:

   • Added trait-level documentation explaining its purpose
   • Documented the crucial D constant
   • Added clear descriptions for generator() and prime_group_order() methods

2. Enhanced test code readability:

   • Replaced the single-letter type alias E with more descriptive EdwardsCurve
   • Maintained all existing test functionality while improving code clarity

These changes make the codebase more maintainable and accessible while adhering to Rust documentation best practices.

PR Checklist

• Added Documentation
• Added Tests (not applicable - documentation changes only)
• Breaking changes (no breaking changes introduced)