Removing return_info argument to env.reset() and deprecated env.seed() function (reset now always returns info) (#2962)

* removed return_info, made info dict mandatory in reset

* tenatively removed deprecated seed api for environments

* added more info type checks to wrapper tests

* formatting/style compliance

* addressed some comments

* polish to address review

* fixed tests after merge, and added a test of the return_info deprecation assertion if found in reset signature

* some organization of env_checker tests, reverted a probably merge error

* added deprecation check for seed function in env

* updated docstring

* removed debug prints, tweaked test_check_seed_deprecation

* changed return_info deprecation check from assertion to warning

* fixes to vector envs, now  should be correctly structured

* added some explanation and typehints for mockup depcreated return info reset function

* re-removed seed function from vector envs

* added explanation to _reset_return_info_type and changed the return statement

tests/vector/utils.py

@@ -63,7 +63,7 @@ class UnittestSlowEnv(gym.Env):
         super().reset(seed=seed)
         if self.slow_reset > 0:
             time.sleep(self.slow_reset)
-        return self.observation_space.sample()
+        return self.observation_space.sample(), {}
 
     def step(self, action):
         time.sleep(action)
@@ -99,7 +99,7 @@ class CustomSpaceEnv(gym.Env):
 
     def reset(self, *, seed: Optional[int] = None, options: Optional[dict] = None):
         super().reset(seed=seed)
-        return "reset"
+        return "reset", {}
 
     def step(self, action):
         observation = f"step({action:s})"