[llvm] [VPlan] Implement VPlan-based cost model for VPReduction, VPExtendedReduction and VPMulAccumulateReduction. (NFC) (PR #113903)

[Sander de Smalen via llvm-commits]

https://github.com/sdesmalen-arm approved this pull request.

Thanks for rebasing @ElvisWang123. Given that this PR is now mostly about flipping the switch to the new cost model, I see no issues with landing it.

https://github.com/llvm/llvm-project/pull/113903