[llvm] [LV] Align legacy cost model to vplan-based model for gather/scatter w/ uniform addr. (PR #155739)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks, with a few additional suggestions to adjust the naming in tests

https://github.com/llvm/llvm-project/pull/155739