This PR allows users to execute queries that refer to attached catalogs from a detached default catalog. This is useful in multi-connection settings.

Say con1's default catalog, db1, is detached and db2 is still attached. Previously, querying a table in db2 from con1 would give a binder error:

-- from con1, gives "Binder Error: Catalog "db1" does not exist!"
FROM db2.tbl; 

To allow the above query, Binder::BindSchemaOrCatalog now uses Catalog::GetCatalogEntry instead of Catalog::GetCatalog to avoid immediately throwing binder exception when default catalog (db1) is not found. This allows the catalog/schema names of db2 to be set properly and go through the rest of binding phase.

Also, we want to throw a sensible error when con1 is referencing some non-existent table in db2. When an entry is not found, DuckDB calls CreateMissingEntryException, which creates default entries in the default catalog (db1). Previously, the error message looked like:

-- "Binder Error: Catalog "db1" does not exist!" 
FROM db2.non_existent_tbl;

-- with fully qualifed path, "Binder Error: Catalog "" does not exist!"
FROM db2.main.non_existent_tbl;

This PR immediately throws a catalog exception when an entry is missing and the default catalog is not attached, avoiding going on to create default entries. Now, it will throw "Catalog Error: Table with name non_existent_table does not exist!"