- Refacor code to remove duplicate code

- Enable async simulation for all vector envs

- Remove `collector.close` and rename `VectorEnv` to `DummyVectorEnv`

The abstraction of vector env changed.

Prior to this pr, each vector env is almost independent.

After this pr, each env is wrapped into a worker, and vector envs differ with their worker type. In fact, users can just use `BaseVectorEnv` with different workers, I keep `SubprocVectorEnv`, `ShmemVectorEnv` for backward compatibility.

Co-authored-by: n+e <463003665@qq.com>
Co-authored-by: magicly <magicly007@gmail.com>