Adding return_info argument to reset to allow for optional info dict as a second return value (#2546)

* 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

tests/vector/test_async_vector_env.py

@@ -40,6 +40,32 @@ def test_reset_async_vector_env(shared_memory):
     assert observations.shape == (8,) + env.single_observation_space.shape
     assert observations.shape == env.observation_space.shape
 
+    try:
+        env = AsyncVectorEnv(env_fns, shared_memory=shared_memory)
+        observations = env.reset(return_info=False)
+    finally:
+        env.close()
+
+    assert isinstance(env.observation_space, Box)
+    assert isinstance(observations, np.ndarray)
+    assert observations.dtype == env.observation_space.dtype
+    assert observations.shape == (8,) + env.single_observation_space.shape
+    assert observations.shape == env.observation_space.shape
+
+    try:
+        env = AsyncVectorEnv(env_fns, shared_memory=shared_memory)
+        observations, infos = env.reset(return_info=True)
+    finally:
+        env.close()
+
+    assert isinstance(env.observation_space, Box)
+    assert isinstance(observations, np.ndarray)
+    assert observations.dtype == env.observation_space.dtype
+    assert observations.shape == (8,) + env.single_observation_space.shape
+    assert observations.shape == env.observation_space.shape
+    assert isinstance(infos, list)
+    assert all([isinstance(info, dict) for info in infos])
+
 
 @pytest.mark.parametrize("shared_memory", [True, False])
 @pytest.mark.parametrize("use_single_action_space", [True, False])