[llvm] [LoopVectorize][NFC] Rewrite tests to check output of vplan cost model (PR #113697)

[David Sherwood via llvm-commits]

david-arm wrote:

Hi @davemgreen, not at all it was a good suggestion and I agree it's worth keeping the more accurate debug output as it's extremely helpful when debugging/understanding vectorisation issues. I'll just fix the tests.

https://github.com/llvm/llvm-project/pull/113697