Enhance function call handling to support nested functions

[TheGupta2012]

Fixes #9

Summary of changes

Added support for nested functions by using qubit transformation for the whole stack of functions. Previously, we were only updating the qubit variables for the latest function call.

Function Call and Argument Handling Improvements

• Added support for nested function calls, allowing functions to call other functions with quantum and classical arguments, including passing quantum registers and parameters through multiple layers of function calls. [1] [2]
• Refactored quantum argument processing by introducing actual_qreg_size_map to accurately track the sizes of actual quantum registers passed to functions, ensuring correct mapping and transformation of qubit arguments. [1] [2] [3] [4] [5] [6]

Quantum Register Transformation

• Updated the quantum register transformation logic in transform_function_qubits and related visitor methods to use both transformation maps and size maps, enabling correct qubit mapping across nested function scopes and supporting more complex function hierarchies. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!