bib: update to images v0.78 and update for API changes

[mvo5]

Two changes:

• The pathpolicy.PathTri type is no longer exported and it is pathpolicy.Pathpolicies instead [0]
• The error messages from images for path policy violations changes and need an update (arguable this is not the best layer to test the error details here and instead we should check how much we can move down to images but that is a followup :)

[0] https://github.com/osbuild/images/pull/854