Make scaffolding Controller more generic

[WeiHaocheng]

We need to do some optimizations to make the Controller more generic, which will help with better modularity.
These changes will not affect the existing API.

• We hope the Controller such as MajorityVoteController can be constructed by any Generation Controller. For a example, the Generation Controller may be a dynasor cot Controller which will yield for different and uncertainly turns between different sample. We develop "parallel_process_helper" to support it. The code looks like:

`

    controllers = [self.generation_controller.clone() for _ in range(sample_num)]

    tasks_list = [[copy.deepcopy(tasks[0])] for _ in range(sample_num)]

    kwargs_list = [kwargs for _ in range(sample_num)]

    yield from parallel_process_helper(controllers, tasks_list, kwargs_list)`

• We make the reward method in BestOfNController more generic as we observe that reward methods become various in recently paper and works.

• We remove most of type check for Task as users may override them.