format: expose triggers in catalog metadata

### What feature or improvement would you like to see?

This is not standard in JDBC/ODBC, but is common across database systems.

- Oracle Database: [ALL_TRIGGERS](https://docs.oracle.com/en/database/oracle/oracle-database/18/refrn/ALL_TRIGGERS.html#GUID-0558FD5E-3EAD-4829-B9A5-4AA029C2105E)
- PostgreSQL: https://github.com/apache/arrow-adbc/issues/3971 (point 7)
- SQL Server: [sys.triggers](https://learn.microsoft.com/en-us/sql/relational-databases/system-catalog-views/sys-triggers-transact-sql?view=sql-server-ver17)

I think it'd be best to add a new function instead of trying to cram this into GetObjects.

Start by reviewing the existing GetObjects API and the linked PostgreSQL issue for the trigger metadata requirements. Define the proposed new function's metadata shape and check how trigger catalogs are exposed by the referenced database systems; done means the API can expose triggers without extending GetObjects.

Written by the indexing model from the issue text.