fix: self overlooked in schema of member functions

[junrushao]

When generation function schema for member functions of a certain class, the existing logics overlooked this as the first argument, which, as a result, generates inproper number of arguments.

More specifically, in the snippet below,

class MyCls {
  void MyFunc(int a);
};

refl::GlobalDef()
    .def_method("MyCls_MyFunc", &MyCls::MyFunc);

the global method MyCls_MyFunc is supposed to have signature (MyCls, int) -> None, but the implementation on mainline gives (int) -> None.

This PR fixes this issue.

[junrushao]

/gemini review

[gemini-code-assist]

Code Review

This pull request correctly addresses an issue where the self argument was overlooked in the schema generation for C++ member functions. The core fix in include/tvm/ffi/function_details.h correctly injects the this pointer type into the argument list. The accompanying test updates in both C++ and Python are thorough and validate the fix. Additionally, the PR includes some unrelated but beneficial changes, such as relaxing type argument constraints in type_info.pxi and adding more test coverage. Overall, this is a solid contribution that improves the correctness and robustness of the FFI reflection system. I have one minor suggestion for a follow-up improvement.