Remove unnecessary declarative wrapper types

Many types in Qt Locations have declarative wrappers through which they are exposed to the QML engine as objects. E.g. QDeclarativeRatings for QPlaceRatings. In practice however, these are value types that don't need to be instantiated by QML code, and instead always come from the engine (via search models etc).

We can convert those types to Q_GADGET, and remove those declarative wrappers. Tests to some degree assume that these properties are of object-type, those need to be adjusted.