Improve codebase to reintegrate cloud tests ASAP.

[koletzilla]

Summary

This PR adds back cloud tests so it will be executed on PRs again. I feel like they are now in a good enough shape to start executing them also in PRs. It also tests with the new CH Cloud cluster which is more stable than the other one.

Pending things:

• https://github.com/ClickHouse/dbt-clickhouse/issues/458: This issue should be closed a few days after we merge this PR, but lets wait a bit in case we found other problematic tests.
• https://github.com/ClickHouse/dbt-clickhouse/issues/532: We need to also test with other python versions. Testing with other versions is currently not the most problematic thing as we do test them in test_matrix, but it would be nice to also have these tests here. We may add these other python versions once we optimise the tests so they run faster or at least they can run concurrently.