cubicweb #10181470 rql2sql doesn't handle FUNC(AGGREGATE(foo)) correctly [in-progress]

It seems the information about needing to aggregate is lost, leading to a UNION in case types are ambiguous, and thus a multi-row rset where a single row was expected.

I'll push a test case shortly.

done in<not specified>
closed by<not specified>
patch[rql2sql/test] add test for wrong transformation [in-progress]