[API Proposal]: Add Tag to Visual3D class

### Background and motivation

Is there any specific reason for not having a object Tag in Visual3D class?
It would be really helpful for interfaces.

### API Proposal

```csharp
namespace System.Windows.Media.Media3D
{
public abstract partial class Visual3D : DependencyObject, DUCE.IResource, IVisual3DContainer
{
public object Tag {get; set;}
}
}
```

### API Usage

```csharp
// Setting Tag to get it somewhere else.
var c = new ModelVisual3D();
c.Tag = "interface";

```

### Alternative Designs

_No response_

### Risks

- Potential issues with binary serialization
- Memory consumption increase by intptr size per Visual3D object.