Move IsDirect = true into DirectPropertyBase (#16256)

Co-authored-by: Max Katz <maxkatz6@outlook.com>
Co-authored-by: Julien Lebosquain <julien@lebosquain.net>

src/Avalonia.Base/DirectProperty.cs

@@ -32,7 +32,6 @@ namespace Avalonia
         {
             Getter = getter ?? throw new ArgumentNullException(nameof(getter));
             Setter = setter;
-            IsDirect = true;
             IsReadOnly = setter is null;
         }
 
@@ -52,7 +51,6 @@ namespace Avalonia
         {
             Getter = getter ?? throw new ArgumentNullException(nameof(getter));
             Setter = setter;
-            IsDirect = true;
             IsReadOnly = setter is null;
         }
 

src/Avalonia.Base/DirectPropertyBase.cs

@@ -28,6 +28,7 @@ namespace Avalonia
             AvaloniaPropertyMetadata metadata)
             : base(name, ownerType, ownerType, metadata)
         {
+            IsDirect = true;
             Owner = ownerType;
         }
 
@@ -43,6 +44,7 @@ namespace Avalonia
             AvaloniaPropertyMetadata metadata)
             : base(source, ownerType, metadata)
         {
+            IsDirect = true;
             Owner = ownerType;
         }