Add more robust testing to streaming ingestion integration tests

[maytasm]

Description

Add more robust testing to streaming ingestion integration tests. Modify the SyntheticStreamGenerator to generate different format of data, including but not limited to invalid format, null/empty data, multi-rows data, etc.

[FrankChen021]

@CaojiamingAlan You can open a new PR to contribute your tests. Thanks for your enthusiasm.