Speed up hatch run lint in CI

[antonymilne]

Our linting GitHub workflow is very slow because it re-installs all the pre-commit environments every time it runs. It block anything because it's not the slowest job we have but it would still be nice to speed up because it should be easy to do so by making a cache in one of two ways:

• use the pre-commit action (probably need to get it approved on our repo to use it?)
• use the cache action

In both cases we need to think about what the cache key should be. Just hashing .pre-commit-config.yaml isn't enough since changes to linter config in pyproject.toml should also invalidate the cache.