* 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
* Move tests to root with automatic PyCharm import refactoring. This will likely fail some tests
* Changed entry point for a registration test env.
* Move a stray lunar_lander test to tests/envs/...
* black
* Change the version from which importlib_metadata is replaced with importlib.metadata. Also requiring installing importlib_metadata for python 3.8 now.
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* Undo last commit
