Properly support multi-project repos when scaffolding

[philliphoff]

Our scaffolding currently expects a repo in which only a single .NET project exists; if more than one, it's not clear which one is being "Dapr-ized". (In particular, it's difficult to deterministically identify a .NET project from a launch configuration, as only the output is specified, which may have a very different path than the project/source that built it.)

We should think about this scenario and determine whether it's worth trying to properly (or, at least, better) support multi-project repos.