Modify vec_gym_env to be compatible with latest version of Gymnasium

[s-casci]

This code modifies vec_gym_env.rs to handle the new step API, like it was done for gym_env.rs. It also makes significant changes to atari_wrappers.py.

In particular, atari_wrappers.py now uses Gymnasium's Vector API, through AsyncVectorEnv, and handles the preprocessing for Atari environments with the AtariPreprocessing wrapper.

The changes were tested with Gymnasium version 0.29.1.

Example usage:

let env = VecGymEnv::new("SpaceInvadersNoFrameskip-v4", 4, Some("/tmp"))?;
env.reset(rng.gen::<u64>())?;
let step = env.step(vec![0i64; 4])?;

where step is now of the following type:

pub struct Step<A> {
    pub states: Vec<Tensor>,
    pub actions: Vec<A>,
    pub rewards: Vec<f64>,
    pub terminated: Vec<bool>,
    pub truncated: Vec<bool>,
}

It might be worth considering modifying vec_gym_env.rs further to allow for non-Atari environments in the future.