[5.5.1] - 2023-02-24

- tests: Refactor helper functions into shared module.
- tests: Use tox to run tests and linter checks instead of using deprecated
  setuptools integration for such tasks.
- setup.py: Drop the unnecessary egg suffix in VCS links.
- setup.py: Remove obsolete setuptools keywords (`tests_require`,
  `setup_requires`, `dependency_links`, ...).
- tox: Use shared `tox.ini` for foris-controller and modules.

- guest: Use correct guest network bridge name for Turris OS 6.0+, so QoS for
  guest network will be able to start again.
- wan: Do not crash when some of the PPPoE credentials options are missing in
  uci config.