Circular dependency in generated code-behind

* .NET Core Version: 5.0.100
* Windows version: Win10-x64
* Does the bug reproduce also in WPF for .NET Framework 4.8?: unknown
* Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)?: maybe, altho i think its more the code generation part.

**Problem description:**
Having two classes `A.B.C.D` and `A.B.C.A` where `A.B.C.D` is a WPF control and also inherits from `A.B.C.A` produces a circular dependency at compile time inside the generated files for the code-behind of `A.B.C.D`.

**Minimal repro:**

Recipes/UI/Pages/Recipes.xaml:
```xml

```
Recipes/UI/Pages/BaseDataGridControls.cs:
```csharp
namespace Recipes.UI.Pages {
public class BaseDataGridControls : Control { ... }
}
```

**Actual behavior:**

Recipes/UI/Pages/Recipes.xaml generates the following Recipes.g.cs :
```csharp
[...]
using Recipes.UI.Pages;
[...]

namespace Recipes.UI.Pages {
[...]
public partial class Recipes : Recipes.UI.Pages.BaseDataGridControls, System.Windows.Markup.IComponentConnector {
[...]
}
[...]
}
```
Which is a circular dependency, since the compiler interprets `Recipes.UI.Pages.BaseDataGridControls` as the class `Recipes`, and not as the namespace. Ironically, the generator also produces the include statement for the namespace, so if the namespace wasn't explicitly specified everything would be fine:
```csharp
[...]
using Recipes.UI.Pages;
[...]

namespace Recipes.UI.Pages {
[...]
//this would work
public partial class Recipes : BaseDataGridControls, System.Windows.Markup.IComponentConnector {
[...]
}
[...]
}
```
I am well aware that the explicit specification is done to avoid collisions that occur more often and this might just be a case of 'don't arrange you classes in this way', but maybe me having encountered the problem warrens the additional complexity in the code generator to detect this case.