feat(UIComponent)!: make GetLayout and GetStyleSheets private

BREAKING CHANGE: UIComponent's GetLayout and GetStyleSheets functions are no longer protected and virtual. Since they are called in UIComponent's constructor, derived classes would not have been fully initialized when the overridden functions are called.

Assets/UIComponents/Core/UIComponent.cs

@@ -98,13 +98,9 @@ protected bool TryProvide<T>(out T instance) where T : class
         {
             return _dependencyInjector.TryProvide(out instance);
         }
-
-        /// <summary>
-        /// Returns the layout loaded in UIComponent's constructor.
-        /// </summary>
-        /// <returns>Component layout</returns>
+
         [CanBeNull]
-        protected virtual VisualTreeAsset GetLayout()
+        private VisualTreeAsset GetLayout()
         {
             var layoutAttribute = LayoutAttributeDictionary[_componentType];
 
@@ -115,12 +111,8 @@ protected virtual VisualTreeAsset GetLayout()
 
             return AssetResolver.LoadAsset<VisualTreeAsset>(assetPath);
         }
-
-        /// <summary>
-        /// Returns the stylesheets loaded in UIComponent's constructor.
-        /// </summary>
-        /// <returns>Component stylesheets</returns>
-        protected virtual StyleSheet[] GetStyleSheets()
+
+        private StyleSheet[] GetStyleSheets()
         {
             var stylesheetAttributes = StylesheetAttributesDictionary[_componentType];