[Zone] Zone State Improvements Part 3 (#4773)

* [Zone State] Additional improvements

* Return early

* Update zone_save_state.cpp

* Push

* Push

* Update zone.cpp

* Update zone_save_state.cpp

* Equip items that were dynamically added on restore

* IsZoneStateValid helper

* ZoneStateSpawnsRepository::PurgeInvalidZoneStates

* Add Zone:StateSaveClearDays and PurgeOldZoneStates

* spawn2 / unique_spawn block when restored from zone state

* One time purge

* Update zone_state_spawns_repository.h

* Update npc.cpp

* Update npc.cpp

* test

* ORDER BY spawn2_id

* Stuff

* Restored corpses shouldn't trigger events

* Fix weird edge case

zone/zone.cpp

@@ -887,7 +887,10 @@ void Zone::Shutdown(bool quiet)
 		c.second->WorldKick();
 	}
 
-	if (RuleB(Zone, StateSavingOnShutdown)) {
+	bool does_zone_have_entities =
+			 zone && zone->IsLoaded() &&
+			 (!entity_list.GetNPCList().empty() || !entity_list.GetCorpseList().empty());
+	if (RuleB(Zone, StateSavingOnShutdown) && does_zone_have_entities) {
 		SaveZoneState();
 	}