`PyType_GetModuleByDef` is really slow.

PyType_GetModuleByDef does a lot of work for what was a single memory read prior to sub-interpreters.

For example, https://github.com/python/cpython/issues/114682.

We should provide a more efficient way to get to the module state from the module def.

AFAICT, the function to get the module state is a pure function of the interpreter and the module def.
Since the module def already has a m_index field that is described as "The module's index into its interpreter's modules_by_index cache.", then a Py_GetModuleFromDef() function could be as simple as:

inline PyObject *
Py_GetModuleFromDef(PyModuleDef *def)
{
     return PyInterpreterState_Get()->modules_table[def->m_base.m_index];
}

Start with PyType_GetModuleByDef, PyModuleDef.m_index, and the interpreter's modules_by_index cache named in the issue. Compare the current lookup path with the proposed module-from-definition API and verify that behavior remains correct per interpreter while addressing the reported overhead.