Draft: Qt Quick Controls 2.0

Task https://phabricator.kde.org/T10168 There are still some minor issues, but it should be playable.

@timotheegiet can you test and check if there are bugs preventing from merging? Also maybe create packages for macos and windows, maybe some paths are to be fixed?

All the activities may be impacted, the major ones being balancebox features and calendar as all the core items have been updated (boxes, sliders...)