DependencyProperty.GetMetadata doesn't handle custom types correctly

[Youssef1313]

Describe the bug

Passing a custom type to DependencyProperty.GetMetadata doesn't get recognized correctly and the returned metadata can have wrong default value.

Steps to reproduce the bug

    public sealed partial class MainWindow : Window
    {
        public MainWindow()
        {
            this.InitializeComponent();
            When_IsTabStop();
        }

        private partial class CustomFE : FrameworkElement { }
        private partial class CustomControl : Control { }
        private partial class CustomUserControl : UserControl { }

        private static class Assert
        {
            public static void IsFalse(bool b)
            {
                if (b)
                {
                    throw new Exception();
                }
            }

            public static void IsTrue(bool b)
            {
                if (!b)
                {
                    throw new Exception();
                }
            }
        }

        public void When_IsTabStop()
        {
            var customControl = new CustomControl();
            Assert.IsTrue(customControl.IsTabStop);

            var userControl = new UserControl();
            Assert.IsFalse(userControl.IsTabStop);

            var customUserControl = new CustomUserControl();
            Assert.IsFalse(customUserControl.IsTabStop);

            Assert.IsFalse((bool)Control.IsTabStopProperty.GetMetadata(typeof(UIElement)).DefaultValue);
            Assert.IsFalse((bool)Control.IsTabStopProperty.GetMetadata(typeof(FrameworkElement)).DefaultValue);
            Assert.IsFalse((bool)Control.IsTabStopProperty.GetMetadata(typeof(CustomFE)).DefaultValue);
            Assert.IsTrue((bool)Control.IsTabStopProperty.GetMetadata(typeof(Control)).DefaultValue);
            Assert.IsFalse((bool)Control.IsTabStopProperty.GetMetadata(typeof(UserControl)).DefaultValue);
            Assert.IsFalse((bool)Control.IsTabStopProperty.GetMetadata(typeof(CustomUserControl)).DefaultValue);
            Assert.IsTrue((bool)Control.IsTabStopProperty.GetMetadata(typeof(CustomControl)).DefaultValue); // fails
        }
    }

Expected behavior

The last assert should pass

Screenshots

No response

NuGet package version

None

Windows version

No response

Additional context

No response