* Update tox.ini to work with tox 4

- remove `skipsdist = True` (tox 4 will not install bandit with this setting, not even in editable mode for environments where `usedevelop = True` is set), add `skip_install = true` to the pep8 job
- remove `requires = tox<4`
- use multi-line list for `passenv`
- add the `-` mark to ignore pylint exit code in the pep8 job - although this mark is already present in `[testenv:pylint]`, tox 4 ignores it when using the `{[testenv:pylint]commands}` substitution

* Use the `tox run` command

In tox 4, environments should always be specified using the -e flag to the `run` subcommand. https://tox.wiki/en/4.4.11/upgrading.html#updating-usage-with-e