[DAGCombine] Deduplicate addcarry node using commutativity.

The first two parameters of addcarry are commutative. We may face a situation where both variant are present in the DAG, in which case we benefit from using just one.

Depends on D57302 and D33587

Reviewed By: RKSimon, chfast

Differential Revision: https://reviews.llvm.org/D57317