Split copy.imageCopier from copy.copier
Split copy.imageCopier from copy.copier

Splits state related to an individual image (i.e. individual
manifest and its edits) from state shared across images in a possible
manifest list.

Does not change anything else about the code structure; cleanups will come later.

Signed-off-by: Miloslav Trmač <9c008e38982a5397deb855345fb164f0558459ae@redhat.com>

containers/image,containers/image