Revert "Revert the Metal Experiment (#701)"

This reverts commit fe1617ffea.

src/Ryujinx.Graphics.Metal/CounterEvent.cs

@@ -0,0 +1,22 @@
+using Ryujinx.Graphics.GAL;
+
+namespace Ryujinx.Graphics.Metal
+{
+    class CounterEvent : ICounterEvent
+    {
+        public CounterEvent()
+        {
+            Invalid = false;
+        }
+
+        public bool Invalid { get; set; }
+        public bool ReserveForHostAccess()
+        {
+            return true;
+        }
+
+        public void Flush() { }
+
+        public void Dispose() { }
+    }
+}