[Feature][Connector-v2] improve assert sink connector

[liugddx]

Close #2796

Purpose of this pull request

improve assert sink connector

Check list

• [ ] Code changed are covered with tests, or it does not need tests for reason:
• [ ] If any new Jar binary package adding in your PR, please add License Notice according New License Guide
• [ ] If necessary, please update the documentation to describe the new feature. https://github.com/apache/incubator-seatunnel/tree/dev/docs