chore(python): add ruff linter as a dependency

[grdddj]

Fixes https://github.com/trezor/trezor-firmware/issues/2820:

• adds ruff linter into shell.nix, so we can run it on python files
• usage - ruff . in core

I could not make it a make command or adding it into pystyle command, it was complaining that ruff: No such file or directory