[llvm] [DAG] Add freeze(assertext(x)) -> assertext(x) folds (PR #94491)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

That said, it's only really a problem for function arguments that aren't noundef; maybe we can just skip emitting AssertZExt for such arguments.

https://github.com/llvm/llvm-project/pull/94491