Add various combines for G_ANYEXT, G_SEXT and G_ZEXT.
Can you add some tests with vectors?
setInstrAndDebugLoc?
Why build a copy instead of CombinerHelper::replaceRegWith?
Committed in https://github.com/llvm/llvm-project/commit/061182b7baf879badc9ff82c88d383d2d9ce279b.