[InstCombine] fold udiv with common shl amount in operands

(X << Z) / (Y << Z) --> X / Y

https://alive2.llvm.org/ce/z/E5eaxU

This fixes the motivating example from issue #58137,
but it is not the most general transform. We should
probably also convert left-shift in the divisor to
right-shift in the dividend for that, but that exposes
another missed canonicalization for shifts and adds.