* Retire stable-rust clippy for buggy redundant_clone * Remove unused scripts/cargo-clippy-stable.sh * Remove clippy-stable from .mergify.yml
* ci: split cargo-clippy into stable and nightly * ci: update mergify
CI uses a number of parameters when running `cargo clippy`. Repeating the same command manually requires some copy/pasting. It is easier when there is a common script that can be run by everyone.