fix(@desktop/chat): sort users by online status

Users model has to be sorted by online status first, otherwise
`UserListPanel` sections will be duplicated. That's because:

> Note: Adding sections to a ListView does not automatically re-order
the list items by the section criteria. If the model is not ordered by
section, then it is possible that the sections created will not be
unique; each boundary between differing sections will result in a
section header being created even if that section exists elsewhere.

fixes: #6563

ui/app/AppLayouts/Chat/panels/UserListPanel.qml

@@ -54,10 +54,16 @@ Item {
 
         model: SortFilterProxyModel {
             sourceModel: usersModule.model
-            sorters: StringSorter {
+            sorters: [
+                RoleSorter {
+                    roleName: "onlineStatus"
+                    sortOrder: Qt.DescendingOrder
+                },
+                StringSorter {
                     roleName: "displayName"
                     caseSensitivity: Qt.CaseInsensitive
                 }
+            ]
         }
         section.property: "onlineStatus"
         section.delegate: (root.width > 58) ? sectionDelegateComponent : null