[applets/systemtray] Fix highlight on applet pin

Sometimes parent component on the applet is not fully updated - for
example effectiveStatus is not yet read from the model. In such case it
will have default value leading to undesired effect.

Call all `updateHighlightedItem` in `Qt.callLater` so that it is called
in next event loop. As a bonus it is called only once, which can improve
performance.

BUG: 437105
FIXED-IN: 5.22.0


(cherry picked from commit 07b3b10de7)

applets/systemtray/package/contents/ui/CurrentItemHighLight.qml

@@ -59,11 +59,11 @@ PlasmaCore.FrameSvgItem {
         target: systemTrayState
 
         function onActiveAppletChanged() {
-            updateHighlightedItem();
+            Qt.callLater(updateHighlightedItem);
         }
 
         function onExpandedChanged() {
-            updateHighlightedItem();
+            Qt.callLater(updateHighlightedItem);
         }
     }
 
@@ -72,7 +72,7 @@ PlasmaCore.FrameSvgItem {
         target: systemTrayState.activeApplet
 
         function onParentChanged() {
-            updateHighlightedItem();
+            Qt.callLater(updateHighlightedItem);
         }
     }
 
@@ -81,11 +81,11 @@ PlasmaCore.FrameSvgItem {
         target: parent
 
         function onWidthChanged() {
-            updateHighlightedItem();
+            Qt.callLater(updateHighlightedItem);
         }
 
         function onHeightChanged() {
-            updateHighlightedItem();
+            Qt.callLater(updateHighlightedItem);
         }
     }
 
@@ -94,7 +94,7 @@ PlasmaCore.FrameSvgItem {
         target: !!highlightedItem && highlightedItem.parent ? highlightedItem.parent : null
 
         function onScaleChanged() {
-            updateHighlightedItem();
+            Qt.callLater(updateHighlightedItem);
         }
     }