[llvm] [RISCV][TTI] Add cost of typebased cast VPIntrinsics with functionalOPC. (PR #97797)

[Luke Lau via llvm-commits]

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lukel97 wrote:

Maybe this is a lot of work but would it be better to just add the vp tests to the existing cast.ll file, so they're all in one place? Since it should just be the same cost as getCastInstrCost

https://github.com/llvm/llvm-project/pull/97797