EXPERIMENTAL: Metal backend (#441)

This is not a continuation of the Metal backend; this is simply bringing
the branch up to date and merging it as-is behind an experiment.

---------

Co-authored-by: Isaac Marovitz <isaacryu@icloud.com>
Co-authored-by: Samuliak <samuliak77@gmail.com>
Co-authored-by: SamoZ256 <96914946+SamoZ256@users.noreply.github.com>
Co-authored-by: Isaac Marovitz <42140194+IsaacMarovitz@users.noreply.github.com>
Co-authored-by: riperiperi <rhy3756547@hotmail.com>
Co-authored-by: Gabriel A <gab.dark.100@gmail.com>

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() { }
+    }
+}