fix(lib): do not take mut self in population.iter()

feat: add into_iter for population

refactor: pass rng as argument

Instead of having the Rng stored
inside the structs, pass it through
the functions. This means it's no longer
necessary to pass perturbations etc. as mutable.

fix: tournament replacement strategy could be using wrong indices

feat: add best replacement

chore: move env to codes/eoa_lib

feat: Add replacement strategy