Carryable NPCs - better support

[LoneBoco]

Carryable NPCs are currently in a weird place and can be improved. Originally, NPCs could be carried across levels, but our current system doesn't really handle that well. I'm not sure if Graal ever handled it well. However, we do have the opportunity to make this robust.

• Improve how NPCs are stored in levels so we can identify if an NPC was carried out of the level.
• If the player is carrying an NPC, send the props on a level change.
• If the NPC is deleted, restore the original NPC in the original level. (Maybe make this a server option)