fix: Inconsistent effect when hover over the new Keyboard Layout applet

Disable blue outline on hover and opaque blue background on press
effects.
Enable highlight on hover for icon representation.

BUG: 432091


(cherry picked from commit 9ade13ea)

applets/keyboardlayout/contents/ui/main.qml

@@ -58,6 +58,7 @@ KeyboardLayoutButton {
             source: icon.name
             visible: display === AbstractButton.IconOnly
             anchors.fill: parent
+            active: hovered
         }
 
         PlasmaComponents3.Label {
@@ -70,6 +71,8 @@ KeyboardLayoutButton {
         }
     }
 
+    background: undefined
+
     // to fit at least 2 letters in systray
     leftPadding: 0
     rightPadding: 0