- move the content of setup.py and pytest.ini to pyproject.toml (eventually, tox.ini will be moved here as well);
- move the version number to a dynamic value in __about__.py;
- temporarily constrain the dependency of pytest to ~=7.0;

- set targeted supported versions to python {3.7, 3.8, 3.9, 3.10} x pytest {7, 8}
- change dependency of pytest to >=7.0,<9.0

- set fail-fast to false (always run on all python versions despite if some of them are failing)
- remove tox's version constrain >=4.19

- add tox-gh to dependency
- remove the incompatible combination py37-pytest8

- upgrade import_path, FixtureRequest to use the newer API

- Add {posargs} to the pytest command in tox.ini
- Fix warning about tool.ruff.lint