message: add union test
diff: @@ -19,6 +19,8 @@ pragma verify_parallelism
  statement ok
  create table integers as select range i from range(100000) order by random()
  +mode skip
  +
  loop i 0 20
  statement ok
  @@ -28,7 +30,44 @@ restart
  # empty result if sorted
  query T
  -select * FROM sorted_integers QUALIFY NOT (i>=lag(i) over () OR lag(i) OVER () IS NULL)
  +select * FROM sorted_integers QUALIFY NOT (i>lag(i) over () OR lag(i) OVER () IS NULL)
  +----
  +
  +
  +statement ok
  +drop table sorted_integers
  +
  +endloop
  +
  +mode unskip
  +
  +# now we do the same but with a UNION ALL
  +
  +loop i 0 20
  +
  +statement ok
  +create table sorted_integers as
  +with p1 as (
  + select i from integers order by i
  +), p2 as (
  + select i + 100000 from integers order by i
  +)
  +select * from p1 union all select * from p2
  +
  +restart
  +
  +query I
  +select * FROM sorted_integers LIMIT 5
  +----
  +0
  +1
  +2
  +3
  +4
  +
  +# empty result if sorted
  +query T
  +select * FROM sorted_integers QUALIFY NOT (i>lag(i) over () OR lag(i) OVER () IS NULL)
  ----
  