[llvm] [llvm][instcombine] Add Missed Optimization for Folding Min Max intrinsic into PHI instruction (PR #84619)

[via llvm-commits]

PeterChou1 wrote:

@dtcxzyw @nikic @goldsteinn 

I think I've accounted for most of changes requested let me know if anything else changed

https://github.com/llvm/llvm-project/pull/84619