[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