Fixes: https://invent.kde.org/plasma/plasma-mobile/-/issues/274
Any feedback on these changes would be much appreciated.


Change Log:
- NanoShell FullScreenOverlay was changed to a LayerShellQt Window to keep it on the top layer and to prevent the popup from obsorbing all touch inputs.
- New animations were added to the volume popup.
- User can now change the volume by touching and dragging on the popup
- The mute button on the popup was fixed
- Mute buttons were added next to the volume sliders in the AudioApplet page
- Volume icons now dynamically update to the volume level
- Visual design adjustments
This allows us in the future to use mobileshell without having the WindowUtil singleton loaded (which does a bunch of wayland calls that aren't necessary for most applications).
Move from a C++ library + QML plugin to a QML plugin only for simplicity, since the homescreen switching architecture will be done from Plasma, and so use of the shell library only needs to be from QML.