[llvm] [LV] Improve cost model for some replicating recipes (PR #192056)

[David Sherwood via llvm-commits]

david-arm wrote:

NOTE: In this PR I've intentionally avoided updating the replicate cost for calls since these are pre-computed using the legacy cost model. In a future PR when I move the call costs over to the vplan model I will update the getScalarizationOverhead call.

https://github.com/llvm/llvm-project/pull/192056