Implement GetRegionCode and add the RegionCode to settings (#999)

This implement `GetRegionCode` accordingly to RE. I've added a setting in the GUI and a field in the Configuration file with a way to update the Configuration file if needed.

Ryujinx.Common/Configuration/ConfigurationFileFormat.cs

@@ -73,6 +73,11 @@ namespace Ryujinx.Configuration
         /// </summary>
         public Language SystemLanguage { get; set; }
 
+        /// <summary>
+        /// Change System Region
+        /// </summary>
+        public Region SystemRegion { get; set; }
+
         /// <summary>
         /// Enables or disables Docked Mode
         /// </summary>