[Mlir-commits] [mlir] [mlir] Use `getSingleElement`/`hasSingleElement` in various places (PR #131460)

[Mehdi Amini]

joker-eph wrote:

> For STLExtras changes, we typically require unit tests and land the change that introduces uses as a follow up PR. 

That could be good practices in general, but that hasn't been very followed here, for example [this one](https://github.com/llvm/llvm-project/pull/84678) was a very similar patch I think (and you were OK on this one as is). 


https://github.com/llvm/llvm-project/pull/131460