Write a lot of small files in s3 when there are two versions schema data in topic

[harveyyue]

Problem

https://github.com/confluentinc/kafka-connect-storage-cloud/issues/520

Solution

Does this solution apply anywhere else?

• [ ] yes
• [ ] no

If yes, where?

Test Strategy

Testing done:

• [ ] Unit tests
• [ ] Integration tests
• [ ] System tests
• [ ] Manual tests

Release Plan

[CLAassistant]

All committers have signed the CLA.