We already parse every image if there's a label filter so that we can
check against the filter, so when we do that, go ahead and read the
OCI-format configuration and inspection data as well, and use an image's
creation date as recorded in inspection data everywhere.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
Avoid parsing metadata that the image library keeps in order to find an
image's top layer and creation date; instead, use the values which the
storage library now makes available, which will be correct once we merge
PR #654 or something like it.
Instead of assuming the last blob which was added for the image was the
manifest, read it directly and compute its digest ourselves.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>