The remote catalog could only drop an empty database: it always asked
the server for a restricted drop.
`DropDatabaseRequest::cascade`, `drop_database(..., cascade=True)` in
Python and `dropDatabase(name, { cascade: true })` in TypeScript ask the
server to drop everything in the database first. The name stays taken
until the server finishes cleaning up the dropped objects' storage. A
restricted drop remains the default.