Merge assemblies into just 'Microsoft.Xaml.Interactivity'

[Sergio0694]

This PR simplifies the solution and merges all assemblies into just 'Microsoft.Xaml.Interactivity'.
There was really no point in us shipping two .dll-s in the same NuGet package anyway.

[michael-hawker]

@Sergio0694 your build is failing similar to my other PR, no idea what's happening, it's complaining about UAP:

2024-11-18T18:32:22.0755175Z "D:\a\XamlBehaviors\XamlBehaviors\src\BehaviorsSDKManaged\BehaviorsSDKManaged.sln" (default target) (1) ->
2024-11-18T18:32:22.0756031Z "D:\a\XamlBehaviors\XamlBehaviors\src\BehaviorsSDKManaged\Microsoft.Xaml.Interactivity.DesignTools\Microsoft.Xaml.Interactivity.DesignTools.csproj" (default target) (6) ->
2024-11-18T18:32:22.0756235Z (EnsureNuGetPackageBuildImports target) -> 
2024-11-18T18:32:22.0758361Z   D:\a\XamlBehaviors\XamlBehaviors\src\BehaviorsSDKManaged\Microsoft.Xaml.Interactivity.DesignTools\Microsoft.Xaml.Interactivity.DesignTools.csproj(105,5): error : This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is ..\packages\Microsoft.VisualStudioEng.MicroBuild.Core.1.0.0\build\Microsoft.VisualStudioEng.MicroBuild.Core.props.
2024-11-18T18:32:22.0758415Z 
2024-11-18T18:32:22.0758420Z 
2024-11-18T18:32:22.0758922Z "D:\a\XamlBehaviors\XamlBehaviors\src\BehaviorsSDKManaged\BehaviorsSDKManaged.sln" (default target) (1) ->
2024-11-18T18:32:22.0759718Z "D:\a\XamlBehaviors\XamlBehaviors\src\BehaviorsSDKManaged\Microsoft.Xaml.Interactivity.Uwp\Microsoft.Xaml.Interactivity.Uwp.csproj" (default target) (8) ->
2024-11-18T18:32:22.0759892Z (_GetSdkToolsPathsFromSdk target) -> 
2024-11-18T18:32:22.0761951Z   C:\Program Files\Microsoft Visual Studio\2022\Enterprise\MSBuild\Microsoft\VisualStudio\v17.0\AppxPackage\Microsoft.AppXPackage.Targets(1181,5): error APPX3217: SDK folder containing 'UAP.props' for 'UAP 10.0.18362.0' cannot be located. See http://go.microsoft.com/fwlink/?LinkID=798187 for more information. [D:\a\XamlBehaviors\XamlBehaviors\src\BehaviorsSDKManaged\Microsoft.Xaml.Interactivity.Uwp\Microsoft.Xaml.Interactivity.Uwp.csproj]

Could there be some service outage or something? We literally just built main fine though before these...