extract OsdSection base component from Volume and Backlight modules

shell/modules/BacklightModule.qml

@@ -4,17 +4,15 @@ import "." as M
 import "../services" as S
 import "../applets" as C
 
-M.BarSection {
+M.OsdSection {
     id: root
     spacing: S.Theme.moduleSpacing
     opacity: S.Modules.backlight.enable && S.BacklightService.available ? 1 : 0
     visible: opacity > 0
-    tooltip: ""
+    _panelHovered: hoverPanel.panelHovered
 
     property int percent: S.BacklightService.percent
-    property bool _osdActive: false
     property bool _percentInit: false
-    readonly property bool _showPanel: root._hovered || hoverPanel.panelHovered || _osdActive
 
     onPercentChanged: {
         if (!_percentInit) {
@@ -22,18 +20,7 @@ M.BarSection {
             return;
         }
         if (percent > 0)
-            _flashPanel();
-    }
-
-    function _flashPanel() {
-        _osdActive = true;
-        _osdTimer.restart();
-    }
-
-    Timer {
-        id: _osdTimer
-        interval: 1500
-        onTriggered: root._osdActive = false
+            flashPanel();
     }
 
     WheelHandler {