More Clippy Fixes, Run Clippy in CI

[rye]

This PR does a number of small changes to resolve clippy lints across the workspace. I'd recommend reviewing it commit-by-commit, since the overall diff is rather large.

A couple of notable things:

• This PR also enables Clippy to run in CI, to hopefully catch future regressions.
• I set up a clippy.toml for geozero to configure the "too-many-arguments" lint threshold to 8 (the default is 7) — this was done to avoid making breaking refactoring changes to the GeomProcessor::coordinate method. (I could just #[allow(..)] it instead if that makes more sense to reviewers.

[pka]

This is great work, thanks! Maybe we should add a sentence about how to run clippy in Readme for ignorants like me?