EventWait should not signal the event when it returns Success (#2739)

* Fix race when EventWait is called and a wait is done on the CPU

* This is useless now

* Fix EventSignal

* Ensure the signal belongs to the current fence, to avoid stale signals

Ryujinx.Graphics.Gpu/Synchronization/SyncpointWaiterHandle.cs

@@ -5,6 +5,6 @@ namespace Ryujinx.Graphics.Gpu.Synchronization
     public class SyncpointWaiterHandle
     {
         internal uint   Threshold;
-        internal Action Callback;
+        internal Action<SyncpointWaiterHandle> Callback;
     }
 }