Deprecate direct invocation of `setup.py`

[Urahara]

I was reading this article: Why you shouldn't invoke setup.py directly that explains why this is not a good practice anymore. I thought about discussing this. Should we change to new approach?

We have only a few places that we directly invoke setup.py so should be an easy task to replace it.

https://github.com/scrapy/scrapy/search?q=setup.py

[wRAR]

So it looks like the only uses are setup.py sdist in tox -e twinecheck and setup.py sdist bdist_wheel in the publish CI action.