[Proposal] Move lab_tasks gym registrations out of __init__.py

[davis-openai]

Proposal

Instead of relying on the recursive import of import_packages() in lab_tasks extension make a registry module that imports environments and registers them. Users should build environments anywhere but would register them all in the same file rather than in various places throughout the extension.

Motivation

By relying on recursive imports through the top level init.py it's not possible to import individual modules from the lab_tasks extension. For instance, if I want to extend an environment in my own extension I have to import the entire lab_tasks extension rather than the specific pieces I need.

Alternatives

• Add registry.py top level module that does the recursive import (and modify that logic) so we can move imports out of init.py

Checklist

• [X] I have checked that there is no similar issue in the repo (required)

Acceptance Criteria

• [ ] Individual modules can be imported from the lab_tasks extension without importing all extension dependencies.
• [ ] Individual modules can be imported from the lab_tasks extension without registering all environments with gym.

[animesh-garg]

this is a very useful suggestion. Thanks @davis-openai

@Mayankm96 @Dhoeller19 This change in import structure would enable lower overhead in users extending existing envs. Thoughts?