v0.3.0
This reduces the amount of work we will do in CI in two ways: - it moves the 'deny warnings' check to happen in the same job as the `cargo test` check, because they both compile at the same optimization level and we can reuse artifacts. - it removes the 'cargo check' job, since any failure there will also be caught in `cargo test`. If jobs were sequential it might be worth checking first, to fail quickly, but since jobs are parallel this is just extra work for no tangible benefit.