[Zone] Implement Zone State Saving on Shutdown (#4715)

* Save spawns

* Update base_zone_state_spawns_repository.h

* Zone state save work

* Code cleanup

* More cleanup

* Database migration

* Update database_update_manifest.cpp

* Revert decay at storage model

* Code cleanup

* More cleanup

* More cleanup

* More cleanup

* Entity variables

* Add entity variables to the schema

* Post rebase

* Checkpoint

* Serialize / deserialize buffs

* Current hp / mana / end save / load

* Save / load current_waypoint

* Add zone spawn protection

* Finishing touches

* Cleanup

* Update zone_save_state.cpp

* Cleanup

* Update zone_save_state.cpp

* Update npc.cpp

* Update npc.cpp

* More

* Update perl_npc.cpp

* Update zone_loot.cpp

common/database_schema.h

@@ -350,6 +350,7 @@ namespace DatabaseSchema {
 			"shared_task_dynamic_zones",
 			"shared_task_members",
 			"shared_tasks",
+			"zone_state_spawns",
 		};
 	}