Add test for self-contained

[tmds]

dotnet/installer#16499 adds the runtime packs for .NET Core and ASP.NET Core.
This makes it possible for a source-build SDK to publish a self-contained application without needing packages from nuget.org.

This issue tracks adding a test for this.

cc @MichaelSimons @mthalman

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[MichaelSimons]

[Triage] the changes coming in #3386 will make it easier to validate the runtime packs are not pulled in from nuget.org during a self-contained test.