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

[Stella Laurenzo via llvm-commits]

stellaraccident wrote:

I'm going to need to hand you over to @makslevental to get this in next week, but this looks reasonable to me.

I think that we should land #117934 first and possibly send out a note telling people with non trivial super projects to use that option. That would require some minor indent-rebasing with this patch.

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