Bring back view package

[tobrun]

In same line as fix for #3755, I would bet better to not use package visibility too much.
Going to try reintroducing the view package.

The following views should be included:

• CompassView
• UserLocationView

[tobrun]

Thinking this a bit more through, I'm going to make subpackage within the maps package and name the package widgets instead of views. Mainly because the package below already contains a View (MapView), and this will introduce the concept of overlain widgets as I was thinking about for #3276.

[tobrun]

To be able to remove package visibility issue, I was obliged exposing this in MapboxMap: