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

[Trevor Gross via llvm-commits]

tgross35 wrote:

Still planning to update this, adding/updating tests just got to me here; the `round` tests really need something like https://github.com/llvm/llvm-project/pull/152662 but that was a bit painful. I have a WIP change adding https://discourse.llvm.org/t/add-matrix-style-preprocessing-to-lit-to-reuse-tests-across-backends/87824 because I figured I'd rather spend time on that than manually smoothing out more tests 🙂 even if that's just for me locally rather than something to actually merge.

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