[improve][api] Support for listing all implementations of a factory

[ashulin]

Purpose of this pull request

Support for listing all implementations of a factory

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

[ashulin]

@EricJoy2048 @Hisoka-X CC