removed inline RandomNumberGenerator implementation

[balisujohn]

Description

Removed inline RandomNumberGenerator implementation and replaced with alias to np.random.Generator.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[XuehaiPan]

Suggested change

	RandomNumberGenerator = np.random.Generator
	RNG = RandomNumberGenerator = np.random.Generator

I think we shall leave the short name convenience (line 137).

[balisujohn]

Sounds good

[RedTachyon]

Is there actually anything preventing us from removing the RandomNumberGenerator abstraction completely, and instead just using np.random.Generator, which it is anyways? The extra layer of (trivial, but still) complexity doesn't seem necessary.

[pseudo-rnd-thoughts]

I think for backward compatibility then we should keep it

[RedTachyon]

In that case, let's keep the synonyms (RNG = RandomNumberGenerator = np.random.Generator), but let's not use them in the code itself. So e.g. the return type of np_random should be Tuple[np.random.Generator, Any] instead of Tuple["RandomNumberGenerator", Any]. This won't break any backwards compatibility because it's the same types, but it will keep the codebase a bit more sane.

[pseudo-rnd-thoughts]

LGTM

[pickettgoogle]

Removing hash_seed from utils/seeding.py breaks gym-retro, which looks for this function there.
The specific line is here:
https://github.com/openai/retro/blob/master/retro/retro_env.py#L214

[pseudo-rnd-thoughts]

You will need to install an older version of gym