Broadcast when the canonical unwrap or applied meshes change. This gets broadcast by utility functions in this class that update those meshes (except for UpdateUnwrapCanonicalOverlayFromPositions, which is usually followed by a more complete update). If those utility functions are not used and the client updates one of those meshes, the client should broadcast the change themselves so that important related info can be updated (for instance, so that the mode can mark those objects as modified).