[llvm] [TTI] Use MemIntrinsicCostAttributes for getGatherScatterOpCost (PR #168650)

[Shih-Po Hung via llvm-commits]

arcbbb wrote:

Parts of getStridedMemoryOpCost uses the gather/scatter path, we’ll update it in the next step, post this patch.

https://github.com/llvm/llvm-project/pull/168650