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

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

So we need instant-UB specifically for calling-convention stuff?  I guess that makes sense.  Do we actually freeze operands to calls to ensure the bits are set correctly, though?

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