More fold to list simplifications

[lue-bird]

List.foldr (::) [] list
--> list

List.foldl (::) [] list
--> List.reverse list

Set.foldr (::) [] set
--> Set.toList set

-- same for foldr, when `expectNaN` is not enabled
Set.foldl Set.insert Set.empty set
--> set

Dict.foldr (\k _ ks -> k :: ks) [] dict
--> Dict.keys dict

Dict.foldr (\_ v vs -> v :: vs) [] dict
--> Dict.values dict

-- same for foldr, when `expectNaN` is not enabled
Dict.foldl Dict.insert Dict.empty dict
--> dict

Dict.foldr (\k v list -> ( k, v ) :: list) Dict.empty dict
--> Dict.toList dict

Includes some nice improvements to normalize.

There are so many more simplifications of this kind (filter, map, fromList, ..., the append ones with flipped arguments, even combining into non-empty accumulator as union, ++ etc). I'll probably try to do something more useful next 😅

[jfmengels]

Looking good so far to me 👍

[jfmengels]

Damn, that's nice! ❤️

[jfmengels]

Beautiful work here @lue-bird, thank you so much for this ❤️