Fix stack overflow in setter

[Blackiris]

Closes #47662
where a Stack overflow happens in the setter.

Currently, if a variable has a setter, every occurrence of its assignments are replaced by the setter, even in its own setter method, thus creating a stack overflow error where the setter method is calling itself recursively.
The is_in_setter = setter_function == codegen.function_name; should detect if the assignement happens in its setter or not, but codegen.function_name is undefined.

This fix fills the codegen.function_name, thus avoiding the bug.

[akien-mga]

Thanks!