Ignore UNKNOWN_DATABASE while obtaining table columns sizes

Why it matters

This feature improves the robustness of the system.columns table by handling cases where some databases may be unknown or inaccessible. Ignoring UNKNOWN_DATABASE errors prevents interruption in obtaining column size information, ensuring more reliable metadata queries.

How to use it

No special configuration is required. The handling of UNKNOWN_DATABASE errors is applied automatically when querying system.columns for table column sizes.