[llvm] [NaryReassociate] Teach NaryReassociate about UniformityAnalysis (PR #175167)

[Pankaj Dwivedi via llvm-commits]

PankajDwivedi-25 wrote:

> There is still the problem that UniformityAnalysis unconditionally requires CycleAnalysis, which causes a measurable performance impact on targets that don't care about divergence: [#99878 (comment)](https://github.com/llvm/llvm-project/pull/99878#issuecomment-2243179679)

Right, let me guard the fetch with hasBranchDivergence.

https://github.com/llvm/llvm-project/pull/175167