Use instance types and preferences in container examples now that common-instancetypes is deployed by default?

[lyarwood]

Is your feature request related to a problem? Please describe:

With v1.4.0 KubeVirt now automatically deploys common-instancetypes. Using instance types and preferences would clean up our example VirtualMachine definitions considerably.

Describe the solution you'd like:

Either entirely switch to or provide instance type and preference based alternatives to the flat example VirtualMachine definitions.

Describe alternatives you've considered:

Additional context:

We already provide default ENV variables for instance types and preferences that could be used here instead of a static instance type or preference matcher.