Refactoring result codes (#731)

* refactoring result codes

- Add a main enum who can handle some orphalin result codes and the default `ResultCode.Success` one.
- Add sub-enum by services when it's needed.
- Remove some empty line.
- Recast all service calls to ResultCode.
- Remove some unneeded static declaration.
- Delete unused `NvHelper` class.

* NvResult is back

* Fix

Ryujinx.HLE/HOS/Services/Am/IHomeMenuFunctions.cs

@@ -18,16 +18,16 @@ namespace Ryujinx.HLE.HOS.Services.Am
 
         [Command(10)]
         // RequestToGetForeground()
-        public long RequestToGetForeground(ServiceCtx context)
+        public ResultCode RequestToGetForeground(ServiceCtx context)
         {
             Logger.PrintStub(LogClass.ServiceAm);
 
-            return 0;
+            return ResultCode.Success;
         }
 
         [Command(21)]
         // GetPopFromGeneralChannelEvent() -> handle<copy>
-        public long GetPopFromGeneralChannelEvent(ServiceCtx context)
+        public ResultCode GetPopFromGeneralChannelEvent(ServiceCtx context)
         {
             if (context.Process.HandleTable.GenerateHandle(_channelEvent.ReadableEvent, out int handle) != KernelResult.Success)
             {
@@ -38,7 +38,7 @@ namespace Ryujinx.HLE.HOS.Services.Am
 
             Logger.PrintStub(LogClass.ServiceAm);
 
-            return 0;
+            return ResultCode.Success;
         }
     }
 }