improve gym speedup

[wangsiping97]

Description

Improved speedup in gym by:

• added max_episode_steps into the base config in c++
• moved max_episode_steps from c++ default config per env into registration.py
• moved trunc computation logics from python to c++

This PR also includes a big refactor of calling test env. We use make_dm / make_gym instead of envpool_cls(spec_cls(spec_cls.gen_config(...))).

Motivation and Context

The computation of trunc in gym_envpool.py is shown as a bottleneck by py-spy.

After fix, envpool's speedup in gym improved from ~1.0x to ~1.3x (using make_gym instead of make_dm for the test below):

Namespace(domain='cheetah', seed=0, task='run', total_step=200000)
100%|███████████████████████████████████████████████████████████████████████████████████████████████| 200000/200000 [00:17<00:00, 11301.86it/s]
FPS(gym) = 11300.15
100%|███████████████████████████████████████████████████████████████████████████████████████████████| 200000/200000 [00:13<00:00, 14408.97it/s]
FPS(envpool) = 14408.43
EnvPool Speedup: 1.28x

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• New environment (non-breaking change which adds 3rd-party environment)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of example)

Implemented Tasks

• moved max_episode_steps from c++ default config per env into registration.py
• moved trunc computation logics from python to c++
• added configuration for max_episode_steps in test files

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.
• I have reformatted the code using make format (required)
• I have checked the code using make lint (required)
• I have ensured make bazel-test pass. (required)

[Trinkle23897]

@wangsiping97 please do the rest the same as my commit

[Trinkle23897]

TODO:

• no_type_check
• docs update