[llvm] [SDag] Notify listeners when deleting a node (PR #66991)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

x86 shuffle combining and SimplifyDemandedVectorElts are very sensitive to oneuse limits - my guess is thatsthe cause of most of the regressions

https://github.com/llvm/llvm-project/pull/66991