691def10a0197d83d2d108bd9043b0916d0f09b4 made all Subquery() instances
equal to each other which broke aggregation subquery pushdown which
relied on object equality to determine which alias it should select.
Subquery.__eq__() will be fixed in an another commit but
Query.rewrite_cols() should haved used object identity from the start.
Refs #30727, #30188.
Thanks Makina Corpus for the report.
Backport of adfbf653dc1c1d0e0dacc4ed46602d22ba28b004 from master
Subquery annotation references must be resolved if they are excluded
from the GROUP BY clause by a following .values() call.
Regression in fb3f034f1c63160c0ff13c609acd01c18be12f80.
Thanks Makina Corpus for the report.
Backport of 42c08ee46539ef44f8658ebb1cbefb408e0d03fe from master
