Fix Label having non-integer sizes

When using a non-integer baseLine, the height can be non-integer, resulting
in non-exact pixel alignments which generate artifacts on the screen.

This happened in Kickoff's LeaveView in Plasma 5.18 (currently used in
openSUSE Leap 15.3) where the focus outline was painted with a different
width in the top and bottom borders due to this pixel misalignment.

src/declarativeimports/plasmacomponents3/Label.qml

@@ -12,6 +12,9 @@ import org.kde.plasma.core 2.0 as PlasmaCore
 T.Label {
     id: control
 
+    height: Math.ceil(implicitHeight)
+    width: Math.ceil(implicitWidth)
+
     verticalAlignment: lineCount > 1 ? Text.AlignTop : Text.AlignVCenter
 
     activeFocusOnTab: false