dispose layout manager when embeddable control root is disposed. (#14341)

src/Android/Avalonia.Android/AvaloniaView.cs

@@ -42,6 +42,13 @@ namespace Avalonia.Android
             set { _root.Content = value; }
         }
 
+        protected override void Dispose(bool disposing)
+        {
+            base.Dispose(disposing);
+            _root?.Dispose();
+            _root = null;
+        }
+
         public override bool DispatchKeyEvent(KeyEvent e)
         {
             return _view.View.DispatchKeyEvent(e);

src/Android/Avalonia.Android/SingleViewLifetime.cs

@@ -15,7 +15,7 @@ namespace Avalonia.Android
             _activity = activity;
 
             if (activity is IAvaloniaActivity activableActivity)
-            {
+            { 
                 activableActivity.Activated += (_, args) => Activated?.Invoke(this, args);
                 activableActivity.Deactivated += (_, args) => Deactivated?.Invoke(this, args);
             }

src/Avalonia.Controls/Embedding/EmbeddableControlRoot.cs

@@ -51,6 +51,11 @@ namespace Avalonia.Controls.Embedding
         }
 
         protected override Type StyleKeyOverride => typeof(EmbeddableControlRoot);
-        public void Dispose() => PlatformImpl?.Dispose();
+
+        public void Dispose()
+        {
+            PlatformImpl?.Dispose();
+            LayoutManager?.Dispose();
+        }
     }
 }