Update build

- Use default github rust version
- Stop using clippy action, it has been unmaintained since 2020
- No longer enforce nightly fmt rules in CI (they can still be enforced
  in commit hooks or nix
- No longer use cargo test unstable options
- Run `cargo clippy --fix` to fix new errors

scripts/run_tests.sh

@@ -6,6 +6,6 @@ set -e
 # We want the code to panic if there is an integer overflow
 export RUSTFLAGS="-C overflow-checks=on"
 
-cargo test --release --all -- -Zunstable-options --report-time
+cargo test --release --all
 cargo test --no-run --features=print-trace
 cargo bench --no-run