Updates the make and registration functions with better parameters and hints

[pseudo-rnd-thoughts]

This PR originally started with fixing the type hints for EnvSpec entry_points where the value could be None by default however this won't work.
After this I looked through the whole file and updated / removed the following sections

1. Updated hint types / field for entry_point in EnvSpec
2. Remove the __relocated__.py file and related code. This error seems old and needed removing at some point
3. Updated make overloads with all environments.
4. Removed EnvRegistry as noted to be removed at 1.0
5. Added all EnvSpec attributes as parameters to gym.register

[pseudo-rnd-thoughts]

@RedTachyon I have readded / kept the make overloads. I investigated testing that the overloads were correct.
However, I found that you need to use the typing_extensions.overload rather than the typing.overload which pycharm doesn't recognise. Therefore, I haven't added testing

def test_make_overloads():
    env_make_hints = {}
    for overloaded_func in typing_extensions.get_overloads(gym.make):
        make_type_hints = typing_extensions.get_type_hints(overloaded_func)
        assert (
            "id" in make_type_hints and "return" in make_type_hints
        ), f"Missing type hints for overloaded `gym.make` id and return, {make_type_hints.get('id', 'unknown env')}"
        if not isinstance(make_type_hints["id"], type):
            for env_id in typing_extensions.get_args(make_type_hints["id"]):
                obs_type, act_type = typing_extensions.get_args(
                    make_type_hints["return"]
                )
                env_make_hints[env_id] = (obs_type, act_type)

    assert (
        env_make_hints.keys() == gym.envs.registry.keys()
    ), f"Missing the make overloads envs: {set(gym.envs.registry.keys()) - set(env_make_hints.keys())}. Additional envs: {set(env_make_hints.keys()) - set(gym.envs.registry.keys())}"
    # todo: add type check on the obs and action type

[arjun-kg]

Looks good apart from a minor change

[arjun-kg]

I assume this should also be "no-entry-point"?

[pzhokhov]

@pseudo-rnd-thoughts would it make sense to make a string constant, say, EMPTY_ENTRY_POINT="no-entry-point" instead of repeating the same string?

[pseudo-rnd-thoughts]

Yes that probaby would have made sense but this is purely in testing and this file alone I believe