More MySQL rewrite rules

[serprex]

1. also remove CAST from OFFSET
2. remove explicit public schema. Needed for UDF passthrough
3. jsonb isn't in MySQL, so rewrite '...'::jsonb literals, in particular mapping [1,2,3] to array for StarRocks

This can be leveraged to use array functions in StarRocks:

CREATE OR REPLACE FUNCTION public.cardinality(jsonb)
RETURNS int AS $$
  BEGIN
    RETURN jsonb_array_length($1);
  END
$$
LANGUAGE PLPGSQL IMMUTABLE;

CREATE OR REPLACE FUNCTION public.array_intersect(jsonb, jsonb)
RETURNS jsonb AS $$
  BEGIN
        RETURN (select jsonb_agg(a) from jsonb_array_elements($1) a join jsonb_array_elements($2) b on a = b);
  END
$$
LANGUAGE PLPGSQL IMMUTABLE;

-- where postgres_fdw is specified in `extensions` option of fdw server
ALTER EXTENSION postgres_fdw ADD FUNCTION public.cardinality(jsonb);
ALTER EXTENSION postgres_fdw ADD FUNCTION public.array_intersect(jsonb, jsonb);

After which select array_intersect(fdwtbl.col, '[1,2,3]') from fdwtbl can be pushed down,
but function will also work if postgres for some reason can't push down