actiondrawer: Cleanup and simplify

Make sure that the view colorset is correct, remove unnecessary layer
(clip is enabled), and remove unnecessary visibility hack for the
notifications widget.

components/mobileshell/qml/actiondrawer/ContentContainer.qml

@@ -27,6 +27,9 @@ Rectangle {
         return Math.max(0, Math.min(1, val));
     }
 
+    Kirigami.Theme.colorSet: Kirigami.Theme.View
+    Kirigami.Theme.inherit: false
+
     // Background color
     color: Qt.rgba(Kirigami.Theme.backgroundColor.r,
                     Kirigami.Theme.backgroundColor.g,

components/mobileshell/qml/actiondrawer/PortraitContentContainer.qml

@@ -93,8 +93,5 @@ Item {
             right: parent.right
         }
         opacity: applyMinMax(root.actionDrawer.offset / root.minimizedQuickSettingsOffset)
-
-        // HACK: there are weird issues with text rendering black regardless of opacity, just set the text to be invisible once it's out
-        visible: opacity > 0.05
     }
 }

components/mobileshell/qml/actiondrawer/quicksettings/QuickSettings.qml

@@ -20,7 +20,6 @@ import org.kde.kirigami 2.20 as Kirigami
  */
 Item {
     id: root
-    layer.enabled: true
     clip: true
 
     required property var actionDrawer