[lint] replace flynt linter with ruff

Summary:
Another dependency dropped, another small gain in performance

For this diff we still don't apply these rules to the Electrum ABC codebase. But now we have the option to apply them incrementally, whereas flynt was a "all or nothing" tool.
Depends on D18907

Test Plan:
ninja all check-all
arc lint --everything

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18913