Apply swh-py-template v0.2.3

pre-commit, tox: Bump black from 19.10b0 to 22.3.0 black is considered stable since release 22.1.0 and the version we are currently using is quite outdated and not compatible with click 8.1.0, so it is time to bump it to its latest stable release. Please note that E501 pycodestyle warning related to line length is replaced by B950 one from flake8-bugbear as recommended by black. https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length Related to T3922

Enable black - blackify all the python files, - enable black in pre-commit, - add a black tox environment.