(#7184) Find actions bound to other versions of Faces.

When we first touch a Face, we load all the available Actions from disk.

Given they define themselves against a specific version of a Face, they are
automatically available tied to the correct version; this makes it trivially
possible to locate those on demand and return them.

Now, we have the ability to find and, consequently, invoke Actions on older
versions of Faces. We don't load enough context, though: the older face will
only have external Actions defined, not anything core.

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