feat: add sing-box TUN dns_mode setting (#10336)

v2rayN/ServiceLib/Models/Configs/ConfigItems.cs

@@ -137,6 +137,7 @@ public class TunModeItem
     public bool EnableIPv6Address { get; set; }
     public string IcmpRouting { get; set; }
     public bool EnableLegacyProtect { get; set; } = true;
+    public string? DnsMode { get; set; }
     public List<string>? RouteExcludeAddress { get; set; }
     public string IPv4Address { get; set; }
     public string IPv6Address { get; set; }

v2rayN/ServiceLib/Models/CoreConfigs/SingboxConfig.cs

@@ -114,6 +114,7 @@ public class Inbound4Sbox
     public bool? auto_route { get; set; }
     public bool? strict_route { get; set; }
     public string? stack { get; set; }
+    public string? dns_mode { get; set; }
     public List<User4Sbox> users { get; set; }
     public List<string>? route_exclude_address { get; set; }
 }