Fail on Clippy errors in CI

[romac]

Once as clippy_check, as configured in .github/workflows/rust.yml, with a JSON output that's not very helpful.

Another time as clippy which produces useful annotations. I am not sure where this one comes from.

I suggest removing the clippy_check job, and while we are at it, turn clippy warnings into CI failures (not sure how to do this, since I don't know where this job is actually set up).

[liamsi]

Another time as clippy which produces useful annotations. I am not sure where this one comes from.

I think the 2nd one is just the output or rather the process that takes the JSON output of the first (the clippy_check action) to annotate the code. But I agree that it would be nice to fail on clippy instead of. Can easily be done by directly calling clippy instead of using the clippy_check action which creates these annotations).

[xla]

Related to #193