Use setup.cfg for python distribution

[mh-northlander]

Static metadata is now recommended.
ref: https://packaging.python.org/tutorials/packaging-projects/#configuring-metadata

[eiennohito]

I don't think that we can do that with Rust. It actually executes non-default Python code to call cargo/rust toolchain to compile Rust module.

[eiennohito]

Also, see https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html, but I don't think that we should move anywhere from setup.py-based installation for the time being.

[mh-northlander]

We still need to use setup.py, but I feel setup.cfg is handy for some metadata like version or readme.

[eiennohito]

Then we also probably should add pypackage.toml with setuptools-rust/wheel dev dependencies written there.