Remove models

This removes:
 - `TrailblockDescription` and friends `ItemTrailblockDescription`, `RunningOrderTrailblockDescription`
 - `TrailblockAgent` and friends `QueryTrailblockAgent` and `ConfiguredTrailblockAgent`

Please note this PR is has got the commit from #2612, which means you can almost entirely ignore what is removed from the Editions as these won't exist in this PR when #2612 gets merged.

Merry Christmas :snowman: :santa: :christmas_tree: