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 selection in case last wins returned wrong index

feat: add best selection

fix: return proper indices from tournament

chore: move env to codes/eoa_lib

refactor: use evaluated population in selection

chore: update explanation comment

feat: add tournament selection