For hypetables that have continuous aggregates, calling drop_chunks now
drops all of the rows in the materialization table that were based on
the dropped chunks. Since we don't know what the correct default
behavior for drop_chunks is, we've added a new argument,
cascade_to_materializations, which must be set to true in order to call
drop_chunks on a hypertable which has a continuous aggregate.
drop_chunks is blocked on the materialization tables of continuous
aggregates