[taskswitcher] Port to KWin script?

Would it make sense to port the task switcher to a KWin script? Seeing how the new desktop "overview" effect seems to be going well, perhaps it would make sense to port the mobile task switcher.

If this were done, the navigation panel should probably remain a containment that can trigger the task switcher effect to open.

Benefits:

• Can make use of KWin scripting API for window thumbnails, desktop switching, etc.
• Infrastructure (seems to?) exist within KWin to implement realtime touch gestures, which would allow us to replace the invisible panel hack currently being used, not sure though if touch edge gestures exist
• Wallpaper blur would be easy to implement https://invent.kde.org/plasma/kwin/-/blob/master/src/effects/overview/qml/ScreenView.qml#L51