Looking for a committer to merge CALCITE-4665: Allow Aggregate.groupSet to contain columns not in any of the groupSets

[xiong duan]

I have a patch <https://github.com/apache/calcite/pull/2458> that has been
reviewed many times since the last month. So I think this PR has been in
good status. So I am looking for a committer to do the final review and
then merge it. Thanks.