Faster `elem` "Hack" for Data.Set?

[PHO]

On 1/30/22 9:59 AM, David Feuer wrote:
[snip]
> . I think the real answer is to remove `elem` from `Foldable` and put
> it somewhere more appropriate.

In a separate class? That would only help `elem` but not any other 
methods of Foldable. I'd rather love to see MonoFoldable[1] to be moved 
to base then.

[1]: 
https://hackage.haskell.org/package/mono-traversable-1.0.15.3/docs/Data-MonoTraversable.html#t:MonoFoldable