[llvm] ISel: introduce vector ISD::LRINT, ISD::LLRINT; custom RISCV lowering (PR #66924)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> Please can you move the tests to a stacked pre-commit so we can see the codegen diff?

Um, wouldn't the tests assert, as I'm using a vector variant of [l]lrint that wouldn't be legal yet?

https://github.com/llvm/llvm-project/pull/66924