[llvm] [mlir] [MLIR][Python] reland (narrower) type stub generation (PR #157930)

[Maksim Levental via llvm-commits]

makslevental wrote:

> For the `error: "__getitem__" method not defined ...`, my next idea would be to use a pattern file. Again, if you think that's a good idea, I can have a stab.

I believe this is because pyright expects some type to be generic - is it the builder classes - in which case a pattern file (or an explicit signature won't help) because they're not generic?

https://github.com/llvm/llvm-project/pull/157930