Bump up python versions

[Alnusjaponica]

Motivation

Resolve https://github.com/optuna/optuna/issues/3964 and https://github.com/optuna/optuna-examples/issues/164

Description of the changes

• Add CI job for python 3.11, (and 3.12 if possible).
• Remove version specification of torch and its families in pytorch/requirements.txt and rl/requirements.txt, due to the impossibility of installing the same version of the necessary libraries in both Python 3.7 and 3.11. See https://github.com/pytorch/pytorch/releases and https://stable-baselines3.readthedocs.io/en/master/misc/changelog.html for reference. ~Please note that the CI job for Python 3.7 has been removed in pytorch and `rl.~

[contramundum53]

@not522 Could you review this PR?