[llvm] [VPlan][test] Fix use-after-free in dumpRecipeInPlan/dumpRecipeUnnamedVPValuesInPlan tests (PR #199275)

[Thurston Dang via llvm-commits]

thurstond wrote:

The diff looks enormous but it's only moving `AI` earlier and scoping `VPlan` to ensure AI outlives the VPlan

https://github.com/llvm/llvm-project/pull/199275