refactor: address TODOs ExtHandle usage and simplify DslIr Ext field opcodes

[Kalpazanova53]

Motivation

This PR introduces extended support for arithmetic operations in the DSL IR, especially for combinations involving Felt and Ext values. The current implementation lacked direct opcodes such as SubFE, MulFEI, and DivFE, which limited expressiveness and required verbose patterns.

Additionally, this PR adds an ext_handle_ptr to the InnerBuilder to facilitate better contextual access from the FeltOperations, improving modularity across builder logic.

Solution

-Added new IR opcodes to DslIr enum:

SubFE, MulFEI, DivFE, enabling direct mixed-type arithmetic.

-Updated builder.rs logic to generate these IR ops where appropriate.

-Modified InnerBuilder to include ext_handle_ptr, ensuring safe access and consistent context passing for extended operations.

-All related // TODO: comments are now removed.

cargo check

cargo build

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes