[RLlib] Add PG torch regression test (#6828)

* Add PG torch regression test to tuned_examples/regression_tests dir.

* Rename cartpole-pg.yaml into cartpole-pg-tf.yaml

* cartpole-pg-tf.yaml: Change cartpole-pg name of tuned_example to cartpole-pg-tf.

doc/source/rllib-algorithms.rst

@@ -213,7 +213,7 @@ Policy Gradients
 
     Policy gradients architecture (same as A2C)
 
-Tuned examples: `CartPole-v0 <https://github.com/ray-project/ray/blob/master/rllib/tuned_examples/regression_tests/cartpole-pg.yaml>`__
+Tuned examples: `CartPole-v0 <https://github.com/ray-project/ray/blob/master/rllib/tuned_examples/regression_tests/cartpole-pg-tf.yaml>`__
 
 **PG-specific configs** (see also `common configs <rllib-training.html#common-parameters>`__):
 

rllib/tuned_examples/regression_tests/cartpole-pg-tf.yaml

@@ -1,4 +1,4 @@
-cartpole-pg:
+cartpole-pg-tf:
     env: CartPole-v0
     run: PG
     stop:

rllib/tuned_examples/regression_tests/cartpole-pg-torch.yaml

@@ -0,0 +1,9 @@
+cartpole-pg-torch:
+    env: CartPole-v0
+    run: PG
+    stop:
+        episode_reward_mean: 150
+        timesteps_total: 100000
+    config:
+        num_workers: 0
+        use_pytorch: true