[llvm] [LV][NFC] Add cost model tests for VPInstructionWithType (PR #200135)

[David Sherwood via llvm-commits]

david-arm wrote:

> Would be good to also include the other cast-case, i.e. single scalar VPReplicateRecipe cast to the tests

I'd prefer to add those in a separate PR if that's ok as they are unrelated to VPInstructionWithType and this PR helps with follow-on PRs.

https://github.com/llvm/llvm-project/pull/200135