Add bindings for PyImport_AddModuleRef and use it in Python::run_code

[ngoldbaum]

Refs #4265.

[mejrs]

Thanks!

[mejrs]

It'd be better to use Bound here (same for the other raw pointers in this function...)

[davidhewitt]

👍 on avoiding the manual reference counting. This can change to

Suggested change

	let mptr = ffi::compat::PyImport_AddModuleRef(ffi::c_str!("__main__").as_ptr());
	let mptr = ffi::compat::PyImport_AddModuleRef(ffi::c_str!("__main__").as_ptr()).assume_owned_or_err(py)?;

It looks like PyModule_GetDict below returns a borrowed reference. Is that problematic under freethreading? I assume so, do we need to call and incref under a critical section? It doesn't look like there is a PyModule_GetDictRef. Should we just do .getattr("__dict__")?

Similarly it looks like PyEval_GetBuiltins is deprecated in 3.13, so I guess we need to update that in a follow up...

[ngoldbaum]

Good call about PyModule_GetDict. I wonder if we don't actually need that on free-threaded builds since we don't need to update globals on Python 3.10 and newer. I'll see if we can avoid it with conditional compilation.

I think we could also probably use PyModule_AddObjectRef or a compat definition based on PyModule_AddObject instead.

[ngoldbaum]

Last push refactors the run_code implementation to use smart pointers and only insert __builtins__ into globals on Python <3.10

[davidhewitt]

Thanks, that's brilliant 👍