Use Instantiator to create drawer actions to improve startup time

Found with qml profiler that the creation of the drawer actions took the most
time. Using an Instantiator is faster and causes the binding to be evaluated
less often. Before the binding inside Kirigami was evaluated 28 times and it was
the thing the most time was spend on, afterwards creating the window is the most
costly operation.
CCBUG:429855

applets/kimpanel/backend/ibus/emojier/emojier.cpp

@@ -165,9 +165,6 @@ public:
         categories.remove({});
         m_categories = categories.values();
         m_categories.sort();
-        m_categories.prepend({});
-        m_categories.prepend(QStringLiteral(":find:"));
-        m_categories.prepend(QStringLiteral(":recent:"));
     }
 
     Q_SCRIPTABLE QString findFirstEmojiForCategory(const QString &category) {

applets/kimpanel/backend/ibus/emojier/ui/emojier.qml

@@ -96,23 +96,17 @@ Kirigami.ApplicationWindow
         collapsed: true
         modal: false
 
-        function createCategoryActions(categories) {
-            var actions = []
-            for(var i in categories) {
-                var cat = categories[i]
-                actions.push(cat === ":recent:" ? recentAction :
-                             cat === ":find:"   ? searchAction :
-                             cat.length === 0   ? allAction
-                                                : categoryActionComponent.createObject(drawer, { category: cat }))
+        Instantiator {
+            model: emoji.categories
+            CategoryAction {
+                category: modelData
+            }
+            onObjectAdded: {
+                var actions = Array.prototype.map.call(drawer.actions, i => i)
+                actions.splice(index + 3, 0, object)
+                drawer.actions = actions
             }
-            return actions;
-        }
-
-        actions: createCategoryActions(emoji.categories)
-
-        Component {
-            id: categoryActionComponent
-            CategoryAction {}
         }
+        actions: [allAction, searchAction, recentAction]
     }
 }