Make audio disposal thread safe on all 3 backends (#2527)

* Make audio disposal thread safe on all 3 backends

* Make OpenAL more consistent with the other backends

* Remove Window.Cursor = null, and change dummy TValue to byte

Ryujinx.Audio.Backends.OpenAL/OpenALHardwareDeviceSession.cs

@@ -190,7 +190,7 @@ namespace Ryujinx.Audio.Backends.OpenAL
 
         protected virtual void Dispose(bool disposing)
         {
-            if (disposing)
+            if (disposing && _driver.Unregister(this))
             {
                 lock (_lock)
                 {
@@ -198,8 +198,6 @@ namespace Ryujinx.Audio.Backends.OpenAL
                     Stop();
 
                     AL.DeleteSource(_sourceId);
-
-                    _driver.Unregister(this);
                 }
             }
         }