krunner: improve the logic of the busy indicator

Only show it after a bit of querying (500ms), disable it as soon as the
query ends.

BUG: 426746

lookandfeel/contents/runcommand/RunCommand.qml

@@ -104,13 +104,14 @@ ColumnLayout {
                 Timer {
                     id: queryTimer
                     property bool queryDisplay: false
-                    running: results.querying || queryDisplay
-                    onRunningChanged: if (running) {
-                        queryDisplay = true
-                    }
-                    onTriggered: if (!results.querying) {
+                    running: results.querying
+                    repeat: true
+                    onRunningChanged: if (queryDisplay && !running) {
                         queryDisplay = false
                     }
+                    onTriggered: if (!queryDisplay) {
+                        queryDisplay = true
+                    }
                     interval: 500
                 }