`rpm-ostree db diff` equivalent

I'm not sure if this is a duplicate, but it'd be very useful to be able to see package changes on bootc the same way that you can see them with `rpm-ostree status` and `rpm-ostree db diff`

Start by comparing bootc's current package-status behavior with the output and semantics of `rpm-ostree status` and `rpm-ostree db diff`. Determine which package changes the proposed equivalent must expose and how users would invoke it; done means bootc can clearly show those changes in a documented, testable form.

Written by the indexing model from the issue text.