[llvm] [SCEV] Updates for getUDivExactExpr() to improve handling of MulExpr numerators/denominators (PR #195704)

[Ryan Buchner via llvm-commits]

bababuck wrote:

Updated to address comments, but best to wait on further review until https://github.com/llvm/llvm-project/pull/195840 is merged and this is rebased on top of that.

https://github.com/llvm/llvm-project/pull/195704