Test refactoring (#2427)

* 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.

???????????

* Undo last commit

tests/envs/robotics/hand/test_manipulate.py

@@ -0,0 +1,26 @@
+import pickle
+
+import pytest
+
+from gym import envs
+from tests.envs.spec_list import skip_mujoco, SKIP_MUJOCO_WARNING_MESSAGE
+
+
+ENVIRONMENT_IDS = (
+    "HandManipulateEgg-v0",
+    "HandManipulatePen-v0",
+    "HandManipulateBlock-v0",
+)
+
+
+@pytest.mark.skipif(skip_mujoco, reason=SKIP_MUJOCO_WARNING_MESSAGE)
+@pytest.mark.parametrize("environment_id", ENVIRONMENT_IDS)
+def test_serialize_deserialize(environment_id):
+    env1 = envs.make(environment_id, target_position="fixed")
+    env1.reset()
+    env2 = pickle.loads(pickle.dumps(env1))
+
+    assert env1.target_position == env2.target_position, (
+        env1.target_position,
+        env2.target_position,
+    )