Port launch feedback KCM to Qt Quick and implement VDG redesign
- Implements VDG mockup M112/364
- But using "Task Manager" naming for consistency instead of "Taskbar"
- Additional UI tweak of using i18np for spinbox suffices
- Switched from generic name "launch" to "launchfeedback"
- This will require i18n pot and doc HTML renames to match
- Original business logic is preserved as-is, but code is simplified and cleaned-up (coding style, etc.)
Depends on D8641.
Reviewers: Plasma, mart
Differential Revision: https://phabricator.kde.org/D8911