chore: replace mypy with pyright

[gruyaume]

Description

Replace mypy with pyright for static analysis

We also leverage this opportunity to use ruff for linting, just like in the other Telco owned projects.

Rationale

• Pyright is now the default static checker in charms.
• It allows us to get rid of the type ignores comment we had for charm library imports.
• It tends to be faster though this does not matter as much.

Reference

• https://github.com/microsoft/pyright
• https://github.com/canonical/charmcraft/blob/main/charmcraft/templates/init-kubernetes/tox.ini.j2

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that validate the behaviour of the software
• [ ] I validated that new and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have bumped the version of the library