Fix weird highlighting behavior of list items in Plasma 6 version of Plasmoid

* Simplify `TopLevelItem` to what is actually needed to make it easier to
  understand
* Use `onEntered` instead of `onContainsMouseChanged` which apparently
  works better (with `onContainsMouseChanged` the selection/highlighting
  did not always work reliably)

plasmoid/package6/contents/ui/TopLevelItem.qml

@@ -1,55 +1,27 @@
 // Based on PlasmaComponents.ListItem from Plasma 5.44.0
-// (Can't use PlasmaComponents.ListItem itself because creating a MouseArea filling
-//  the entire entire item for detecting right-mouse-click is not possible due to binding
-//  loop of width and height properties.)
 import QtQuick 2.7
-import QtQuick.Layouts 1.1
 import org.kde.ksvg 1.0 as KSvg
 import org.kde.kirigami 2.20 as Kirigami
 
 Item {
     id: listItem
-    property bool expanded: false
     default property alias content: paddingItem.data
-
-    /**
-     * If true makes the list item look as checked or pressed. It has to be set
-     * from the code, it won't change by itself.
-     */
-    //plasma extension
-    //always look pressed?
-    property bool checked: false
-
-    /**
-     * If true the item will be a delegate for a section, so will look like a
-     * "title" for the otems under it.
-     */
-    //is this to be used as section delegate?
-    property bool sectionDelegate: false
-
-    /**
-     * type: bool
-     * True if the separator between items is visible
-     * default: true
-     */
+    property bool expanded: false
     property bool separatorVisible: true
 
     width: parent ? parent.width : childrenRect.width
     height: paddingItem.childrenRect.height + background.margins.top + background.margins.bottom
-
     implicitHeight: paddingItem.childrenRect.height + background.margins.top
                     + background.margins.bottom
 
-    function activate(containsMouse) {
-        view.activate(containsMouse ? index : -1)
+    function activate() {
+        view.activate(index)
     }
 
     KSvg.FrameSvgItem {
         id: background
         imagePath: "widgets/listitem"
-        prefix: (listItem.sectionDelegate ? "section" : (itemMouse.pressed
-                                                         || listItem.checked) ? "pressed" : "normal")
-
+        prefix: "normal"
         anchors.fill: parent
         visible: listItem.ListView.view ? listItem.ListView.view.highlight === null : true
         Behavior on opacity {
@@ -69,20 +41,18 @@ Item {
             top: parent.top
         }
         height: naturalSize.height
-        visible: separatorVisible && (listItem.sectionDelegate
-                                      || (typeof (index) != "undefined"
-                                          && index > 0 && !listItem.checked
-                                          && !itemMouse.pressed))
+        visible: separatorVisible && (index !== undefined
+                                  && index > 0 && !listItem.checked
+                                  && !itemMouse.pressed)
     }
 
     MouseArea {
         id: itemMouse
         property bool changeBackgroundOnPress: !listItem.checked
-                                               && !listItem.sectionDelegate
         anchors.fill: background
         hoverEnabled: true
         acceptedButtons: Qt.LeftButton | Qt.RightButton
-
+        onEntered: listItem.activate()
         onClicked: function(mouse) {
             switch (mouse.button) {
             case Qt.LeftButton:
@@ -96,10 +66,6 @@ Item {
             }
         }
 
-        onContainsMouseChanged: {
-            listItem.activate(containsMouse)
-        }
-
         Item {
             id: paddingItem
             anchors {