Changes Default Value of multiple_joins_rewriter_version to 2

Why it matters

This update improves the query rewriting process for multiple joins by leveraging knowledge of column names. It enhances query optimization and correctness when dealing with complex joins, providing better performance and more reliable query execution for users.

How to use it

Users can enable this feature by setting multiple_joins_rewriter_version to 2. Since the default value has been changed to 2, the new rewriter is enabled by default in this ClickHouse version. To explicitly set it, use:

SET multiple_joins_rewriter_version = 2;