bindings/python: Use implicit namespaces

bindings/python: Use implicit namespaces

The use of 'namespace_packages' is deprecated [1] and for Python >= 3.3,
implicit/native namespaces should be used. There are no incompatibilities
as we require Python >= 3.8. More details can be found in [2] and [3].

[1] https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
[2] https://packaging.python.org/en/latest/guides/packaging-namespace-packages/
[3] https://peps.python.org/pep-0420/