This PR focus on some definition change of trainer to make it more friendly to use and be consistent with typical usage in research papers, typically change `collect-per-step` to `step-per-collect`, add `update-per-step` / `episode-per-collect` accordingly, and modify the documentation.
Bipedal-Hardcore-SAC
- Our default choice: remove the done flag penalty, will soon converge to ~280 reward within 100 epochs (10M env steps, 3~4 hours, see the image below)
- If the done penalty is not removed, it converges much slower than before, about 200 epochs (20M env steps) to reach the same performance (~200 reward)