Add an operator to split the positive/negative outputs to two ports / add the info in a new column

[Yicong-Huang]

There are some tasks to do labeling according to a condition. For example, the below workflow does a regex match and label the matched ones with "pos" and "neg" otherwise. Ideally, we can do such thing in one Operator.

[zuozhiw]

Discussion 2022.05.19: low priority, good for undergrad task

[Xiao-zhen-Liu]

Discussion 2022.12.07: Low priority.

[shengquan-ni]

Low priority.