Support CASCADE dropping relations

[damian3031]

In dbt core, get_drop_sql drops relations with CASCADE - all downstream models are dropped.
For example, if if you rundbt seed --full-refresh, seed is first dropped together with downstream models (source).

Currently we do not support it, so user need to manually drop downstream models.

Best solution would be to add it in Trino, I created issue for that trinodb/trino#19498