[llvm] [C API] Add support for setting/getting new nneg flag on zext instructions (PR #73592)

[Benji Smith via llvm-commits]

Benjins wrote:

Not sure what the issue with the build is: the only test failure is in the Window's build in `TEST 'MLIR :: python/dialects/scf.py'`, which shouldn't be affected by these changes. I can try merging from main if we want to make it green before landing, otherwise is this good to merge in?

https://github.com/llvm/llvm-project/pull/73592