Core, Test: Refactor tests to support ClickHouse Cloud

[mzitnik]

Summary

Add Cloud test according to @pan3793 development https://github.com/pan3793/spark-clickhouse-connector/tree/cloud-test

Checklist

Delete items not relevant to your PR:

• [ ] Unit and integration tests covering the common scenarios were added
• [ ] A human-readable description of the changes was provided to include in CHANGELOG
• [ ] For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[pan3793]

overall lgtm if tests pass, just small nits. thanks for making it work

[mzitnik]

Thanks, @pan3793 yes we have some improvements that we need to make

[pan3793]

we'd better fix the flaky issues before merging to keep the CI stable ...

sorry, it's midnight in my timezone, I have to go to bed now, will take another look tomorrow

[mzitnik]

When we run it locally, it works perfectly. Maybe somehow related to the Github