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.HLE/HOS/SystemState/SystemStateMgr.cs

@@ -37,6 +37,8 @@ namespace Ryujinx.HLE.HOS.SystemState
 
         internal long DesiredLanguageCode { get; private set; }
 
+        internal uint DesiredRegionCode { get; private set; }
+
         public TitleLanguage DesiredTitleLanguage { get; private set; }
 
         internal string ActiveAudioOutput { get; private set; }
@@ -79,6 +81,11 @@ namespace Ryujinx.HLE.HOS.SystemState
             }
         }
 
+        public void SetRegion(SystemRegion region)
+        {
+            DesiredRegionCode = (uint)region;
+        }
+
         public void SetAudioOutputAsTv()
         {
             ActiveAudioOutput = AudioOutputs[0];