Add cargo check in the CI and make it fail if cargo check fails

[lovesh]

No description provided.

[bddap]

cargo-build already performs all the same checks as cargo-check so this wouldn't do anything by itself. cargo-check does a subset of what cargo build does.

cargo-clippy could be useful but it currently fails due wasm build trickery.

If we want to fail CI when there are warnings, cargo rustc -- -Dwarnings would work. We could also use RUSTFLAGS="-D warnings" cargo build as mentioned in https://github.com/rust-unofficial/patterns/blob/master/anti_patterns/deny-warnings.md .

[bddap]

We can add RUSTFLAGS="-D warnings" to our unit tests if we want CI to fail on warnings.