Do not collapse projects in CombineUnions if it hasCorrelatedSubquery

SPARK-37915 added CollapseProject in rule CombineUnions, but it shouldn't collapse projects that contain correlated subqueries since haven't been de-correlated (PullupCorrelatedPredicates).

Here is a simple example to reproduce this issue

SELECT (SELECT IF(x, 1, 0)) AS a
FROM (SELECT true) t(x)
UNION 
SELECT 1 AS a 

Exception:

java.lang.IllegalStateException: Couldn't find x#4 in []