Fix column projection for union all queries with multiple aliases

create table source1 (dt string, d1 int, d2 int) stored as orc;
create table source2 (dt string, d1 int, d2 int) stored as orc;
insert into source1 values ('20211107', 1, 2);
insert into source2 values ('20211108', 11, 22);

select explode(map('D219', D219
,'D220', D220)) as (key, value) from (
   {{select '20211107' as date_key
,1 as D219
,2 as D220
) t}}
union all
select explode(map('D221', D221
,'D222', D222)) as (key, value)
from (}}
  {{select '20211107' as date_key
,1 as D221
,2 as D222
) t

1
2
11
22

D219 1
D220 2
D221 11
D222 22