ComboBox: paint focus border if combobox component itself is focused (instead of internal text field) or if client property JComponent.focusOwner is set

Theme Editor:
- do not set client property `JComponent.focusOwner` on internal components of combobox and spinner
- repaint preview on window activation (necessary because if something changed in editor and switching to another app, the editor is saved and the preview is updated while the editor window is not-active, which hides all focus indicators)

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatComboBoxUI.java

@@ -670,6 +670,9 @@ public class FlatComboBoxUI
 	/** @since 1.3 */
 	public static boolean isPermanentFocusOwner( JComboBox<?> comboBox ) {
 		if( comboBox.isEditable() ) {
+			if( FlatUIUtils.isPermanentFocusOwner( comboBox ) )
+				return true;
+
 			Component editorComponent = comboBox.getEditor().getEditorComponent();
 			return (editorComponent != null) ? FlatUIUtils.isPermanentFocusOwner( editorComponent ) : false;
 		} else