in `./bins/inbreeding/`, this MR does
- refactor the "list item drawing" from `environment.rs` and `strategy.rs` into the `draw_unique_elements` function of new `random.rs` module
- use a `HashSet` to draw unique indices in the slice of "things" to draw from and then extracts the items corresponding to these indices

## results
```bash
use ./bins/inbreeding
use std bench

const PRNG_SEED = 0
const OPTS = {
    nb_bytes: (10 * 1_024),
    k: 10,
    n: 20,
    nb_measurements: 100,
    nb_scenarii: 10,
    measurement_schedule: 1,
    measurement_schedule_start: 2_000,
    max_t: 2_000,
    strategies: [ "single:5" ],
    environment: null,
}

def run [rev: string] {
    git co $rev

    inbreeding build

    let a = bench --rounds 5 {
        inbreeding run --options ($OPTS | update environment "fixed:0") --prng-seed $PRNG_SEED
    }
    let b = bench --rounds 5 {
        inbreeding run --options ($OPTS | update environment "fixed:1") --pr...