Add nonroot variant for language-specific images

[EronWright]

In #237 we added a "non-root" variant to the kitchen-sink image. Please provide the same for the language-specific images.

Use case: the Pulumi Kubernetes Operator prefers to run the Pulumi deployment operations in a "restricted" pod, that is a low-trust pod. The Operator also allows the user to select (and customize) the image. It would be nice to be able to use the language-specific images.

[JonCholas]

Any progress on this? why wouldn't pulumi push the same image but just with specific language on it?