[llvm] [VPlan] Materialize VPFirstOrderRecurrencePHIRecipe start value in VPlan (PR #171590)

[Luke Lau via llvm-commits]

lukel97 wrote:

Do we still prefer https://github.com/llvm/llvm-project/pull/172009? I think that patch seems to be aligned with the general trend of breaking up recipes as we get closer to lowering

https://github.com/llvm/llvm-project/pull/171590