It seems that most uses of these folds should be strict left folds
(I could only find a single place that benefits from a right fold).
So this removes the existing setFold/mapFold/mapFoldWihKey
replaces them with:
- setFoldl/mapFoldl/mapFoldlWithKey (strict left folds)
- setFoldr/mapFoldr (for the less common case where a right fold actually makes sense, e.g., CmmProcPoint)
Signed-off-by: Michal Terepeta <firstname.lastname@example.org>