Move TemplateBinding to Avalonia.Base.

It would be useful to be able to access it from here to provide bindings in default template values, and it has no dependency on XAML.

src/Avalonia.Base/Properties/AssemblyInfo.cs

@@ -6,6 +6,7 @@ using Avalonia.Metadata;
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Animation")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Animation.Easings")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Controls")]
+[assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Data")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Data.Converters")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Input")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Input.GestureRecognizers")]

tests/Avalonia.Markup.Xaml.UnitTests/XamlTestBase.cs

@@ -13,7 +13,7 @@ namespace Avalonia.Markup.Xaml.UnitTests
         public XamlTestBase()
         {
             // Ensure necessary assemblies are loaded.
-            var _ = typeof(TemplateBinding);
+            var _ = typeof(Binding);
             GC.KeepAlive(typeof(ItemsRepeater));
             if (AvaloniaLocator.Current.GetService<AvaloniaXamlLoader.IRuntimeXamlLoader>() == null)
                 AvaloniaLocator.CurrentMutable.Bind<AvaloniaXamlLoader.IRuntimeXamlLoader>()