pkg/api/handlers is used for type definitions by pkg/bindings,
i.e. podman-remote; a libimage dependency means that podman-remote
would also include libimage.
Instead, move the ImageDataToImageInspect function close to the
only user (and make it private).
[NO NEW TESTS NEEDED]: Only moves unchanged code (apart from a required
warning fix), should not change behavior.
Signed-off-by: Miloslav Trmač <mitr@redhat.com>