gh-117142: Slightly hacky fix for memory leak of StgInfo (GH-119424)

gh-117142: Slightly hacky fix for memory leak of StgInfo (GH-119424)

Add a funciton that inlines PyObject_GetTypeData and skips
type-checking, so it doesn't need access to the CType_Type object.
This will break if the memory layout changes, but should
be an acceptable solution to enable ctypes in subinterpreters in
Python 3.13.

Mark _ctypes as safe for multiple interpreters

Co-authored-by: neonene <53406459+neonene@users.noreply.github.com>