Parallelize Rust function apply_givens_rotation_in_place

[kevinsung]

This loop here:

ffsim/src/gates/orbital_rotation.rs

Line 45 in 1e55524

Zip::from(&slice1).and(&slice2).for_each(|&i, &j| {

A straightforward attempt doesn't pass the compiler because each thread needs to have mutable references to two rows of the array being modified. We know that no two threads will have access to the same rows, but the compiler can't tell.