Fix groupmate obs, add tests

ml-agents/mlagents/trainers/poca/optimizer_torch.py

                 seq_obs.append(_self_obs[start:end])
             self_seq_obs.append(seq_obs)
 
-            for groupmate_obs, team_action in zip(obs, actions):
+            for groupmate_obs, groupmate_action in zip(obs, actions):
-                for (_obs,) in groupmate_obs:
-                    first_seq_obs = _obs[start:end]
-                    seq_obs.append(first_seq_obs)
+                for _obs in groupmate_obs:
+                    sliced_seq_obs = _obs[start:end]
+                    seq_obs.append(sliced_seq_obs)
-                _act = team_action.slice(start, end)
+                _act = groupmate_action.slice(start, end)
                 groupmate_seq_act.append(_act)
 
             all_seq_obs = self_seq_obs + groupmate_seq_obs

ml-agents/mlagents/trainers/tests/torch/test_poca.py

     }
 
     trainer_settings.network_settings.memory = (
-        NetworkSettings.MemorySettings(sequence_length=16, memory_size=10)
+        NetworkSettings.MemorySettings(sequence_length=8, memory_size=10)
         if use_rnn
         else None
     )

ml-agents/mlagents/trainers/tests/torch/test_ppo.py

 
     trainer_settings = attr.evolve(dummy_config)
     trainer_settings.network_settings.memory = (
-        NetworkSettings.MemorySettings(sequence_length=16, memory_size=10)
+        NetworkSettings.MemorySettings(sequence_length=8, memory_size=10)
         if use_rnn
         else None
     )
     optimizer = create_test_ppo_optimizer(
         dummy_config, use_rnn=rnn, use_discrete=discrete, use_visual=visual
     )
+    # Time horizon is longer than sequence length, make sure to test
+    # process trajectory on multiple sequences in trajectory + some padding
     time_horizon = 15
     trajectory = make_fake_trajectory(
         length=time_horizon,