[llvm] [LV]: Add costs to VPInstruction (PR #125008)

[Hassnaa Hamdi via llvm-commits]

hassnaaHamdi wrote:

> Could you please add a test case, some more details of what VPInstructions need costs now and how this is related to the change for interleaving?

I already tried to 

https://github.com/llvm/llvm-project/pull/125008