misc: chore: Pass rainbow color by reference in the event instead of passing around a packed int.

src/Ryujinx.Common/Helpers/RefEvent.cs

@@ -0,0 +1,58 @@
+using Gommon;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace Ryujinx.Common.Helper
+{
+    public class RefEvent<T>
+    {
+        public delegate void Handler(ref T arg);
+        
+        private readonly Lock _subLock = new();
+        private readonly List<Handler> _subscriptions = [];
+    
+        public bool HasSubscribers
+        {
+            get
+            {
+                lock (_subLock)
+                    return _subscriptions.Count != 0;
+            }
+        }
+
+        public IReadOnlyList<Handler> Subscriptions
+        {
+            get
+            {
+                lock (_subLock)
+                    return _subscriptions;
+            }
+        }
+
+        public void Add(Handler subscriber)
+        {
+            Guard.Require(subscriber, nameof(subscriber));
+            lock (_subLock)
+                _subscriptions.Add(subscriber);
+        }
+
+        public void Remove(Handler subscriber)
+        {
+            Guard.Require(subscriber, nameof(subscriber));
+            lock (_subLock)
+                _subscriptions.Remove(subscriber);
+        }
+
+        public void Clear()
+        {
+            lock (_subLock)
+                _subscriptions.Clear();
+        }
+
+        public void Call(ref T arg)
+        {
+            foreach (Handler subscription in Subscriptions)
+                subscription(ref arg);
+        }
+    }
+}