Use Qt Quick Controls 2 in examples written in Qt Quick

With the move of the Qt Quick Controls 2 module into the qtdeclarative repository it becomes easier to use our standard controls and layouts in examples written in Qt Quick. Qt Quick Controls 2 are what we want application developers to use to build their Qt UIs.

So we should do so in all examples (across all modules) that are written in Qt Quick, and are not primarily about showing how to do custom UI development, or how to use the low-level Qt Quick primitives.

This follows up on the work done in QTBUG-90878.