[llvm] [InstCombine] Fold `lshr -> zext -> shl` patterns (PR #147737)

[via llvm-commits]

zGoldthorpe wrote:

@nikic @arsenm @dtcxzyw should I request a review from someone else, or is there a deficiency in my current implementation?

https://github.com/llvm/llvm-project/pull/147737