Integrating Gymnasium

[Markus28]

This PR leaves gym as it is and adds gymnasium environments in an analogous way.

[Markus28]

This implementation leaves the Gym envpool part entirely unmodified. My changes add a Gymnasium option, which mostly mirrors the Gym option. Specs now have the additional attributes gymnasium_action_space and gymnasium_observation_space. The attributes action_space and observation_space remain reserved for Gym, preserving backward compatibility.
I will still have to add some tests and play around with it locally to make sure that everything works as expected. Also, the documentation needs to be updated accordingly.

Were these roughly the changes we had in mind @Trinkle23897? I hope I understood you correctly on discord :).

[Trinkle23897]

That makes sense! I’ll take a look these days. Great job and huge thanks!

[mavenlin]

@Trinkle23897 Would it be better that we can make this less verbose? e.g. with a helper function like

def register_to_py(cpp_shared_lib):
  dict_of_name_to_env = py_env(cpp_shared_lib)
  globals().update(dict_of_name_to_env)
  __all__ = dict_of_name_to_env.keys()

[mavenlin]

I mean, we could make this change as a separate PR after this one.

[Trinkle23897]

Sounds good to me