[Feature] Support to delete the row in aggregation merge engine

[Aitozi]

Search before asking

• [X] I searched in the issues and found nothing similar.

Motivation

Currently, the aggregation merge engine only produce INSERT row. However, if all the input of a key has been retract, it should produce a DELETE row.

Solution

No response

Anything else?

No response

Are you willing to submit a PR?

• [X] I'm willing to submit a PR!