[llvm] [SelectionDAG] Add `f16` soft promotion for `lrint` and `lround` (PR #152684)

[Folkert de Vries via llvm-commits]

folkertdev wrote:

The uncommented tests fail if globalisel is not also changed, so I think it makes sense to keep them combined.

https://github.com/llvm/llvm-project/pull/152684