[llvm] [VPlan] Run narrowInterleaveGroups during general VPlan optimizations. (PR #149706)

[Emilio Cota via llvm-commits]

cota wrote:

Hi @fhahn,
This PR is causing downstream failures for JAX. In particular, after pulling this commit I'm seeing egregious numerical errors when computing a Hessian with JAX on CPU. Any guesses as to why that may be?

https://github.com/llvm/llvm-project/pull/149706