Use pg_get_serial_sequence to detect auto incrementing columns

[koskimas]

We currently have our own hacky version of this detection on postgres that fails if someone renames the column.

CREATE TABLE foo (id SERIAL, val TEXT);
SELECT pg_get_serial_sequence('foo', 'id'); 
-- 'public.foo_id_seq'
ALTER TABLE foo RENAME COLUMN id TO identifier;
SELECT pg_get_serial_sequence('foo', 'identifier');
-- 'public.foo_id_seq' <-- this is correct! The sequence is not renamed
SELECT pg_get_serial_sequence('foo', 'val');
-- NULL