support ATTACH statement for Iceberg catalog (similar to UC_CATALOG)

[mike-luabase]

The uc_catalog extension supports the following:

INSTALL uc_catalog from core_nightly;
INSTALL delta from core;
LOAD delta;
LOAD uc_catalog;
CREATE SECRET (
	TYPE UC,
	TOKEN '${UC_TOKEN}',
	ENDPOINT '${UC_ENDPOINT}',
	AWS_REGION '${UC_AWS_REGION}'
)
ATTACH 'test_catalog' AS test_catalog (TYPE UC_CATALOG)
SHOW ALL TABLES;
SELECT * FROM test_catalog.test_schema.test_table;

This would be extremely helpful to have for Iceberg.

[samansmink]

hey @mike-luabase yea supporting more catalogs in this way is definitely something we are looking into, the iceberg catalog seems like a sensible candidate for sure