Tooling upgrades

[jodal]

• Require Python 3.11+
• Replace pkg_resources with importlib.metadata
• Move project declaration to pyproject.toml
• Change project layout
• Replace flake8 and black with ruff
• Format with ruff
• Autofix with ruff
• Autofix with ruff --unsafe-fixes
• Manually fix ruff lints

[jodal]

Rebased on top of today's release now, and added the version simplification related to mopidy/mopidy#2153.