Reuse ClickHouseTestHelpers module in ClickHouseTestRunner

What does this MR do and why?

This MR does some clean up of the new ClickHouse migration-related code:

• Reuses ClickHouseTestHelpers module in ClickHouseTestRunner, so that ClickHouseTestRunner depends on ClickHouseTestHelpers instead of the other way around;
• Fixes the VERBOSE setting of the rake tasks. This was happening because rake tasks get prepended the Rake::FileUtilsExt which already contains a verbose attribute.

Part of #428124 (closed)

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Numbered steps to set up and validate the change are strongly suggested.

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