[InstCombine] Add reverse of ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub...

[InstCombine] Add reverse of ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub nuw (Y >>u exact Z) (#91386)

This is the same fold as ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub
nuw (Y >>u exact Z), which we already have and approved in the codebase, but with the sub operands
swapped.

Proof it works in reverse, so we could have a wider generalization of this pattern: https://alive2.llvm.org/ce/z/2cRcdx