fix: PrintVisualTree using StringBuilderCache

src/Avalonia.Base/Avalonia.Base.csproj

@@ -37,6 +37,7 @@
     <InternalsVisibleTo Include="Avalonia.Win32, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Web.Blazor, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Dialogs, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Diagnostics, PublicKey=$(AvaloniaPublicKey)"/>
     <InternalsVisibleTo Include="DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7" />
   </ItemGroup>
 

src/Avalonia.Diagnostics/Diagnostics/VisualTreeDebug.cs

@@ -2,6 +2,7 @@ using System;
 using System.Text;
 using Avalonia.Controls;
 using Avalonia.Data;
+using Avalonia.Utilities;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Diagnostics
@@ -10,9 +11,9 @@ namespace Avalonia.Diagnostics
     {
         public static string PrintVisualTree(IVisual visual)
         {
-            var result = new StringBuilder();
+            var result = StringBuilderCache.Acquire();
             PrintVisualTree(visual, result, 0);
-            return result.ToString();
+            return StringBuilderCache.GetStringAndRelease(result);
         }
 
         private static void PrintVisualTree(IVisual visual, StringBuilder builder, int indent)