sql: inverted index on array types

[jordanlewis]

This issue tracks adding an inverted index access method (GIN index in Postgres) for array types.

The encoding for these should be a simpler version of what we have for JSON inverted indexes. The index should be usable to satisfy queries of the form:

CREATE TABLE a (a INT PRIMARY KEY, b INT[];
SELECT * FROM a WHERE $1 = ANY(b)

with a tight index span.

The optimizer should also be able to plan zigzag joins against these indexes when there's a conjunction of this form.