SB3 v1.6.2: Progress bar and RL Zoo3 package

SB3 Contrib: https://github.com/Stable-Baselines-Team/stable-baselines3-contrib
RL Zoo3: https://github.com/DLR-RM/rl-baselines3-zoo

New Features:

• Added progress_bar argument in the learn() method, displayed using TQDM and rich packages
• Added progress bar callback

RL Zoo3

• The RL Zoo can now be installed as a package (pip install rl_zoo3)

Bug Fixes:

• self.num_timesteps was initialized properly only after the first call to on_step() for callbacks
• Set importlib-metadata version to ~=4.13 to be compatible with gym=0.21

Deprecations:

• Added deprecation warning if parameters eval_env, eval_freq or create_eval_env are used (see #925) (@tobirohrer)

Others:

• Fixed type hint of the env_id parameter in make_vec_env and make_atari_env (@AlexPasqua)

Documentation:

• Extended docstring of the wrapper_class parameter in make_vec_env (@AlexPasqua)