New windowing system

Large commit that totally refactor of the way we handle the bar and
panels.

Testing should focus on Panels, Bar, Keyboard Focus, IPC calls.

Changes brief:
- One NFullScreenWindow per screen which handle it's bar and dedicated
panels.
- Added shadows
- Reintroduced dimming
- New panels animations
- Proper Z ordering
- Panels on overlay laywer is not reimplemented, if we do it then the
bar will be on the Overlay too
- Panel dragging was not reimplemented, to be discussed before
reimplementing
- Still a WIP, need to work more on shadows and polishing + debugging.

Modules/ControlCenter/Widgets/Notifications.qml

@@ -10,6 +10,6 @@ NIconButtonHot {
   icon: Settings.data.notifications.doNotDisturb ? "bell-off" : "bell"
   hot: Settings.data.notifications.doNotDisturb
   tooltipText: I18n.tr("quickSettings.notifications.tooltip.action")
-  onClicked: PanelService.getPanel("notificationHistoryPanel")?.toggle(this)
+  onClicked: PanelService.getPanel("notificationHistoryPanel", screen)?.toggle(this)
   onRightClicked: Settings.data.notifications.doNotDisturb = !Settings.data.notifications.doNotDisturb
 }