Refactor shaders to improve code readability and reduce redundancy

[moven0831]

Problem

The current Metal shader code, particularly in the bigint, field, and curve directories, is becoming increasingly complex and difficult to maintain. There's a lot of boilerplate code, especially around passing and using the prime modulus, and the lack of structure makes it harder to reason about the code. This issue proposes a refactoring of the shader code as follow.

Introduce Classes

Wrap the core data structures (e.g., BigInt, Jacobian, Affine) into proper classes. This will allow us to associate methods with the data, improving code organization.

Overload Operators

Implement operator overloading for these classes (e.g., +, -, *, >=, etc.) to make the code more readable and less verbose. This will reduce the need for explicit function calls like bigint_add_unsafe(), ff_add(), mont_cios(), etc.

Abstract Prime Modulus

Currently, the prime modulus is passed as an argument to many functions. We should abstract this away, possibly by making it a member of a FieldElement class or a template parameter, to avoid redundant code and improve readability.

Acceptance criteria

1. New classes are created:
   • BigInt class for big integer arithmetic
   • FieldElement class for field elements modulo p
   • JacobianPoint and AffinePoint classes for elliptic curve points
   • Key operators are overloaded for these types
2. Modulus is abstracted:
   • p is a static property of FieldElement class
   • Functions no longer take p as a redundant parameter
3. Kernel functions refactored:
   • Use new classes instead of raw BigInt values
   • Update function signatures to match
4. Shader tests pass:
   • Existing shader tests still pass with refactored code
   • Add any missing tests for edge cases