Fortress, medieval and Ancient athens fixes

[MotionlessTrain]

Closes #
Closes #

Changes proposed in this pull request

• Followup to Medieval and Fortress fixes and Shire and Fortress rebalancing in 1.20.1 #10364.
  In the fix of the decorations not being shown as levellable in the build tool, it turned out that the decoration controller broke,
  as I forgot to set a pack in the fixed decorations. I thought including a path and schematicName would be enough to tell the decoration controller to not use the legacy code anymore, but it was looking at the pack NBT-component instead.
• I've been thinking about removing the legacy code in TileEntityDecorationController as well,
  as the decorations for which that was still needed should now all be migrated. But I wasn't sure whether that would be better in a separate PR
  Edit: I didn't check whether it would be needed in Stylecolonies, as a few styles there (at least Frontier) stems from before 1.19
• Move the medium_military harbour pier decoration in Ancient athens to the correct folder

Testing

• Yes I tested this before submitting it.
• I also did a multiplayer test.

Review please