(#7184) Load the core of obsolete versions of Faces.

When we define an action on an older version of a Face, we must be sure to
directly load the core of that version, not just define it with the external
Action(s) that it had.

Otherwise we break our contract, which is that any core Actions for a specific
version will be available to your external Action for as long as we support
that core version.

Reviewed-By: Pieter van de Bruggen <pieter@puppetlabs.com>