Add several convenient ways to resolve root

Why it matters

This feature simplifies the way users specify and locate the root metadata.json file when working with Iceberg tables. By providing more flexible resolution options, it reduces configuration complexity and potential errors, improving user experience and integration with Iceberg tables.

How to use it

Users can now reference the Iceberg table's root metadata.json file through several new approaches in the table function and engine configurations. The exact usage depends on the chosen method, but generally involves pointing to the Iceberg table location or directly specifying the metadata.json path in the query or table definition.