Replace lint tools with Ruff - #412

Includes #411.

Re: (2) at #409 (comment)

This replaces a lot of the lint tools with Ruff.

Some of them had no effect, || true meant they never failed. In this PR, I've applied the changes, for example for isort and pyupgrade.

A follow-up PR can replace some more tools. For example, Black also has || true, so it has quite a lot of formatting to make. We can check this separately because it touches many lines.

The Ruff config is in pyproject.toml. I also Ruff to .pre-commit-config.yaml for a few reasons:

• it pins the Ruff version so we can upgrade it with intention and don't get surprising failures
• it makes it easy to run it via the CI
• it's easy to add other non-Ruff linting to this file
• those who want to can install the https://pre-commit.com CLI locally and have it run Ruff before committing