* initial draft of optional info dict in reset function, implemented for cartpole, tests seem to be passing
* merged core.py
* updated return type annotation for reset function in core.py
* optional metadata with return_info from reset added for all first party environments, with corresponding tests. Incomplete implementation for wrappers and vector wrappers
* removed Optional type for return_info arguments
* added tests for return_info to normalize wrapper and sync_vector_env
* autoformatted using black
* added optional reset metadata tests to several wrappers
* added return_info capability to async_vector_env.py and test to verify functionality
* added optional return_info test for record_video.py
* removed tests for mujoco environments
* autoformatted
* improved test coverage for optional reset return_info
* re-removed unit test envs accidentally reintroduced in merge
* removed unnecessary import
* changes based on code-review
* small fix to core wrapper typing and autoformatted record_epsisode_stats
* small change to pass flake8 style
