In #20538, I was asked to consider refactoring the new OCI pull code
from within the generic machine directory. This is something I had
tried when originally coding it but it became apparent that a much
larger refactor to prevent circular deps was needed. Because I did not
want to pollute the initial PR with that refactor, I asked for the PR to
merge first. This is the refactor that needed to be done.
Signed-off-by: Brent Baude <bbaude@redhat.com>