Add Map.fromSetMaybe and Map.fromSetMaybeA

Consider adding

```hs
fromSetMaybe :: (k -> Maybe a) -> Set k -> Map k a
fromSetMaybeA :: Applicative f => (k -> f (Maybe a)) -> Set k -> f (Map k a)
```

This looks like a small piece that is missing and would work well with #1227 for something like

```hs
generateMaybeMissingSet :: Applicative f => (k -> Maybe a) -> WhenMissingSet f k a
```