Investigate PEP517 and the setuptools new recomendation to build/distribuite packages

[beraldoleal]

From setuptools quickstart guide:

The landscape of Python packaging is shifting and Setuptools has evolved to only provide backend support, no longer being the de-facto packaging tool in the market. All python package must provide a pyproject.toml and specify the backend (build system) it wants to use. The distribution can then be generated with whatever tools that provides a build sdist-alike functionality. While this may appear cumbersome, given the added pieces, it in fact tremendously enhances the portability of your package. The change is driven under PEP 517. ...

IMO, this could be useful to solve a few problems we have today related to easily distributing Avocado properly and also making clear and concise build targets.

This is related to #4372, #4357 and #4336