Revert "Use CP_SMALL_TLIST for hash aggregate"
This reverts commit
4cad2534da6d17067d98cf04be2dfc1bda8f2cd0 due to a
performance regression. It will be replaced by a new approach in an
upcoming commit.
Reported-by: Andres Freund
Discussion: https://postgr.es/m/
20200614181418.mx4bvljmfkkhoqzl@alap3.anarazel.de
Backpatch-through: 13