Get dz safe return from cache not db

This was loading the dz from database to get safe return data every time
a client's dz removal timer triggered

Add the Zone::GetDynamicZone() method so zones that are dz instances can
find the data from the cache of any dz systems

zone/zone.cpp

@@ -2714,3 +2714,21 @@ bool Zone::IsZone(uint32 zone_id, uint16 instance_id) const
 {
 	return (zoneid == zone_id && instanceid == instance_id);
 }
+
+DynamicZone Zone::GetDynamicZone()
+{
+	if (GetInstanceID() == 0)
+	{
+		return {}; // invalid
+	}
+
+	auto expedition = Expedition::FindCachedExpeditionByInstanceID(GetInstanceID());
+	if (expedition)
+	{
+		return expedition->GetDynamicZone();
+	}
+
+	// todo: tasks, missions, and quests with an associated dz for this instance id
+
+	return {}; // invalid
+}