[CS7069] Reference to type 'Color' claims it is defined in 'System.Drawing.Common', but it could not be found`
## 🐛 Bug Report
  
I am migrating from MomoAndroid10 to .NET6 and upgrade MvvmCross from version 8.0.2 to 9.0.10

Extending MvxColorValueConverter got the below build errors:

```
[CS0508] 'TextColorByPopupStyleValueConverter.Convert(PopupStyle, object, CultureInfo)': return type must be 'Color' to match overridden member 'MvxColorValueConverter<PopupStyle>.Convert(PopupStyle, object?, CultureInfo?)'
[CS7069] Reference to type 'Color' claims it is defined in 'System.Drawing.Common', but it could not be found
```

Try going to the assembly of **System.Drawing.Color** refers to /usr/local/share/dotnet/shared/Microsoft.NETCore.App/6.0.16/System.Drawing.Primitives.dll (*)

![Screenshot 2023-06-16 at 17 32 26](https://github.com/MvvmCross/MvvmCross/assets/55356231/31f58661-0c3c-4fc3-826d-3a3d12f018ea)

I try adding a NuGet reference to [System.Drawing.Common(6.0.0)](https://www.nuget.org/packages/System.Drawing.Common/6.0.0) in the Android project, but still error and  the **System.Drawing.Color** still reference to (*). I think it prefers to use the assembly from .NET6

I try building and got errors both on VS 22 and VS 22 for Mac

I don't find any example of MvxColorValueConverter after version 9 is released. 

### Expected behavior 

**System.Drawing.Color** use namespace System.Drawing in assembly System.Drawing.Primitives 

(System.Drawing.Primitives.dll)

### Reproduction steps

- Create an Android library project
- Extend MvxColorValueConverter class
- Build on VS 2022

### Configuration

NET SDK 6.0.408 
NET Runtime 6.0.16

**Version:** 9.0.10

**Platform:** 
- [ ] :iphone: iOS
- [x] :robot: Android
- [ ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [ ] :monkey: Xamarin.Forms
