Background

In #132, we gave Lab libraries the ability to declare dependencies under UWP, WinAppSdk and Uno under both WinUI 2 and 3.

The problem

However, we didn't provide a way for test projects to declare dependencies the same way. This means that if a test project needs a nuget package that uses WinUI, they would need to add it to their lab source project, even if that project never used it.

The solution

Allow UI test projects to include WinUI 2/3 dependencies in the same way as #132 did.