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/Notification/NotificationHistoryPanel.qml

@@ -12,9 +12,8 @@ import qs.Widgets
 NPanel {
   id: root
 
-  preferredWidth: 380
-  preferredHeight: 480
-  panelKeyboardFocus: true
+  preferredWidth: 380 * Style.uiScaleRatio
+  preferredHeight: 480 * Style.uiScaleRatio
 
   onOpened: function () {
     NotificationService.updateLastSeenTs()