优化更新代码，添加界面功能并整合

WPFluent/Controls/TreeModelListView/TreeRowExpander.cs

@@ -0,0 +1,12 @@
+using System.Windows;
+using System.Windows.Controls;
+
+namespace WPFluent.Controls;
+
+public class TreeRowExpander : ContentControl
+{
+    static TreeRowExpander()
+    {
+        DefaultStyleKeyProperty.OverrideMetadata(typeof(TreeRowExpander), new FrameworkPropertyMetadata(typeof(TreeRowExpander)));
+    }
+}