Rewrite miri script in Rust 

Per https://github.com/rust-lang/miri/pull/2381#pullrequestreview-1045199136 and https://github.com/rust-lang/miri/pull/2877, a [miri script](https://github.com/rust-lang/miri/commit/798e6e13b6122c85599790a49f076221aad8849b) written in Rust would be more portable. 