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/System/Region.cs

@@ -0,0 +1,13 @@
+namespace Ryujinx.Configuration.System
+{
+    public enum Region
+    {
+        Japan,
+        USA,
+        Europe,
+        Australia,
+        China,
+        Korea,
+        Taiwan
+    }
+}