CALL_FUNCTION_EX argument passing routine can be improved for vectorcalls

While working on https://github.com/python/cpython/issues/95126, I noticed that CALL_FUNCTION_EX for vectorcall Python functions is extremely wasteful. These are its steps:

1. CALL_FUNCTION_EX calls do_call_core with a args tuple and kwargs dict.
2. Eventually it's detected that the function supports vectorcall, and it calls _PyVectorcall_Call. This calls _PyStack_UnpackDict, which unpacks the args tuple and kwargs dict into a C array.
3. This C array is passed to the vectorcall function. Eventually calling _PyEval_Vector.
4. _PyEval_Vector calls _PyEvalFramePushAndInit, which sees that there's complex args, and recreates the tuple and args dict in initialize_locals from the C array.
5. Frame is pushed and evaluated, then popped. End.

We shouldn't even be converting the arguments to a C array just to vectorcall. We should instead directly transfer ownership of args tuple and kwds dict because that would be significantly faster in this case (and save us the tuple and dict recreation dance).

CC @markshannon and @brandtbucher .

Trace the argument flow through do_call_core, _PyVectorcall_Call, _PyStack_UnpackDict, _PyEval_Vector, _PyEvalFramePushAndInit, and initialize_locals. First understand how CALL_FUNCTION_EX reaches vectorcall Python functions and how ownership is handled at each boundary. Done means the path avoids the intermediate C array and tuple/dict recreation while preserving correct argument ownership and behavior.