Add support for custom PAC and proxy script paths

Introduces options to specify custom PAC file and system proxy script paths for system proxy settings. Updates configuration models, view models, UI bindings, and logic for Linux/OSX proxy handling and PAC management to use these custom paths if provided. Also adds UI elements and localization for the new settings.

v2rayN/ServiceLib/Resx/ResUI.Designer.cs

@@ -3508,6 +3508,24 @@ namespace ServiceLib.Resx {
             }
         }
         
+        /// <summary>
+        ///   查找类似 Custom PAC file path 的本地化字符串。
+        /// </summary>
+        public static string TbSettingsCustomSystemProxyPacPath {
+            get {
+                return ResourceManager.GetString("TbSettingsCustomSystemProxyPacPath", resourceCulture);
+            }
+        }
+        
+        /// <summary>
+        ///   查找类似 Custom system proxy script file path 的本地化字符串。
+        /// </summary>
+        public static string TbSettingsCustomSystemProxyScriptPath {
+            get {
+                return ResourceManager.GetString("TbSettingsCustomSystemProxyScriptPath", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   查找类似 Allow Insecure 的本地化字符串。
         /// </summary>