The old implementation only counted full images when sharing content
between them. That is wrong, the store is layer based. We can have two
images with no parent image that shares layers.
As such get rid of the image tree that only is able to walk child/parent
images. Instead we actually walk all layers now and correctly notice
when they are shared.
To this this correctly, first convert all layers to map so we can look
them up by ID. And add missing size information if needed. Then we walk
all images layers and count how often each layers is used. Then walk
again but this time we know if the layer size must be shared or not so
we can actually acount things correctly.
Fixes: containers/podman#24452
Fixes: https://issues.redhat.com/browse/RHEL-29641
Signed-off-by: Paul Holzinger <pholzing@redhat.com>
Paul Holzinger