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

[Stella Laurenzo via llvm-commits]

stellaraccident 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.

There are differences that I've bridged by writing various helpers, mostly around array and buffer protocols. Then the way that constructors are modeled is wholly better but different. I found that when retrofitting, there are usually a few places that leave you scratching your head on how to do the same thing. But when writing fresh, the nanobind way is more powerful. 

I think it's kind of nice to do what Peter is doing here and getting it in universe first. Removes some activation energy for taking it the rest of the way.

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