[llvm] [DAGCombiner] Preserve nneg flag from inner zext when we combine (z/s/aext (zext X)) (PR #82199)

[Craig Topper via llvm-commits]

topperc wrote:

> > The changes LGTM, but is it possible to test it (or at least some parts of it)?
> 
> Patch now contains changes to one of the tests from #82227. That tests the code in getNode(ISD::ANY_EXTEND

Added two more tests to covert getNode for ISD::SIGN_EXTEND and ISD::ZERO_EXTEND.

https://github.com/llvm/llvm-project/pull/82199