Encourage users to use optimal base images

[richlander]

By default, we give users Debian base images. That's the correct choice because Debian is the .NET default. However, many users likely don't know that there are other choices. We have an opportunity to tell them.

We could/should print a new informational message in the case that the user does not override/customize inferencing (e.g. no ContainerFamily).

Something like:

Info: See http://aka.ms/dotnet/sdk/containers to learn how to reduce the size of your container images