Reduce the number of examples

As a user, it would be easier to pick from 3 than 50 examples/tutorials. We have a large number of examples/tutorials, from which evaluators can choose. However, which ones should evaluators pick up. Currently, we highlight some examples, but it is still difficult for the evaluator to pick up the most relevant ones. We should show only a few most relevant examples/tutorials and have a button/UI control to show more of them.

We would need to set priorities for the examples in Qt. The priority could be based on the usage frequency from our online doc stats or Qt telemetry. Or if we have a similar example with a widget and QML UI, the latter one would have higher priority.