Add --python flag for 3.10 / 3.11 support (3.12 too unstable for some use-cases)

[s-smits]

tpux --is_tpu_pod n --install_zsh y --add_path_to_shell_config y --python 3.10

[yixiaoer]

Thanks for your feedback! The TPU environment is intended for development, so we want to encourage users to always develop based on the latest version. If there's a need for different versions, you can create and install different Python versions or set up venv.