[llvm] [LoopVectorize] Use CodeSize as the cost kind for minsize (PR #124119)

[John Brawn via llvm-commits]

john-brawn-arm wrote:

> Looks like this was causing some test failures due to it not begin rebased to the latest main before merging, which missed some tests updates. Should be fixed in [649f4dc](https://github.com/llvm/llvm-project/commit/649f4dcc1930ab5aa338c0f1b13ebb16767be400).

Thanks for fixing that.

https://github.com/llvm/llvm-project/pull/124119