am: Implement GetHealthWarningDisappearedSystemEvent (#1788)

This implement IApplicationFunctions GetHealthWarningDisappearedSystemEvent call which is needed by Mario Kart 8 in Chinese version. Call was checked by RE.
We still have to determine where to signals some AM events.

Thanks to Kakasita on our Discord to reported this and confirm this works fine!

Ryujinx.HLE/HOS/Services/Am/AppletOE/ApplicationProxyService/ApplicationProxy/IApplicationFunctions.cs

@@ -27,16 +27,20 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletOE.ApplicationProxyService.Applicati
         private KEvent _gpuErrorDetectedSystemEvent;
         private KEvent _friendInvitationStorageChannelEvent;
         private KEvent _notificationStorageChannelEvent;
+        private KEvent _healthWarningDisappearedSystemEvent;
 
         private int _gpuErrorDetectedSystemEventHandle;
         private int _friendInvitationStorageChannelEventHandle;
         private int _notificationStorageChannelEventHandle;
+        private int _healthWarningDisappearedSystemEventHandle;
 
         public IApplicationFunctions(Horizon system)
         {
+            // TODO: Find where they are signaled.
             _gpuErrorDetectedSystemEvent         = new KEvent(system.KernelContext);
             _friendInvitationStorageChannelEvent = new KEvent(system.KernelContext);
             _notificationStorageChannelEvent     = new KEvent(system.KernelContext);
+            _healthWarningDisappearedSystemEvent = new KEvent(system.KernelContext);
         }
 
         [Command(1)]
@@ -521,5 +525,22 @@ namespace Ryujinx.HLE.HOS.Services.Am.AppletOE.ApplicationProxyService.Applicati
 
             return ResultCode.Success;
         }
+
+        [Command(160)] // 9.0.0+
+        // GetHealthWarningDisappearedSystemEvent() -> handle<copy>
+        public ResultCode GetHealthWarningDisappearedSystemEvent(ServiceCtx context)
+        {
+            if (_healthWarningDisappearedSystemEventHandle == 0)
+            {
+                if (context.Process.HandleTable.GenerateHandle(_healthWarningDisappearedSystemEvent.ReadableEvent, out _healthWarningDisappearedSystemEventHandle) != KernelResult.Success)
+                {
+                    throw new InvalidOperationException("Out of handles!");
+                }
+            }
+
+            context.Response.HandleDesc = IpcHandleDesc.MakeCopy(_healthWarningDisappearedSystemEventHandle);
+
+            return ResultCode.Success;
+        }
     }
 }