[DAG] foldAddToAvg - optimize nested m_Reassociatable matchers (#171681)
The use of nested m_Reassociatable matchers by #169644 can result in
high compile times as the inner m_Reassociatable call is being repeated
a lot while the outer call is trying to match. Place the inner
m_ReassociatableAnd at the beginning of the pattern so it is not
repeatedly matched in recursion.