[BUG] top_level.txt is incorrect when `ext_package` is set

setuptools version

setuptools==65.0.0

Python version

python 3.10.4

OS

ubuntu 22.04

Additional environment information

appears independent of environment

Description

when ext_package is used, any ext_modules show up in top_level.txt (though they should not)

Expected behavior

I expect the contents of top_level.txt to respect ext_package -- in the below example I should only see a in top_level.txt

How to Reproduce

install this and then inspect top_level.txt

# ==> a/__init__.py <==
from . import _hello_world

# ==> _hello_world.c <==
#include <Python.h>

static PyObject* _hello_world(PyObject* self) {
    return PyUnicode_FromString("hello world");
}

static struct PyMethodDef methods[] = {
    {"hello_world", (PyCFunction)_hello_world, METH_NOARGS},
    {NULL, NULL}
};

static struct PyModuleDef module = {
    PyModuleDef_HEAD_INIT,
    "_hello_world",
    NULL,
    -1,
    methods
};

PyMODINIT_FUNC PyInit__hello_world(void) {
    return PyModule_Create(&module);
}

# ==> setup.py <==
from setuptools import setup, Extension

setup(
    name="a",
    version="1",
    packages=["a"],
    ext_package="a",
    ext_modules=[
        Extension(
            '_hello_world',
            ['_hello_world.c'],
            py_limited_api=True,
            define_macros=[('Py_LIMITED_API', None)],
        ),
    ],
)

Output

$ virtualenv venv
...
$ venv/bin/pip install .
...
$ cat venv/lib/*/site-packages/a-1.dist-info/top_level.txt
_hello_world
a

Start with the setup.py example and trace how ext_package and ext_modules contribute to the generated top_level.txt in the installed dist-info directory. Reproduce the install, inspect the generated file, and verify that it contains a while excluding _hello_world when ext_package is set.