We found that when we have window functions and also correlated subqueries in the
same target list, the CQueryMutators::NormalizeWindowProjList method would leave
the varattno attributes of outer references in the subquery unchanged. That needs
to be changed, since we are producing a different RTE for the query.

We will eventually create a fix. For now, this PR just searches for the
problem and triggers a fallback when we see it, to avoid incorrect results.
Co-authored-by: NAbhijit Subramanya <asubramanya@pivotal.io>
Co-authored-by: NHans Zeller <hzeller@vmware.com>