[llvm] [mlir] [mlir python] Add nanobind support for standalone dialects. (PR #117922)

[Maksim Levental via llvm-commits]

makslevental wrote:

FWIW I think we could just wholesale switch to `nanobind`. Prior, I wasn't sure what the feature disparities were but I've been writing a new set of bindings this week and it looks to me like it's all there and basically spelled exactly the same.

https://github.com/llvm/llvm-project/pull/117922