Fully disconnect gamepad handler for rainbow color if configuration is set with UseRainbowLed false

Also check if its even enabled before setting the rainbow color
Fixes strobing

src/Ryujinx.Common/Utilities/Rainbow.cs

@@ -5,17 +5,29 @@ namespace Ryujinx.Common.Utilities
 {
     public class Rainbow
     {
-        public const float Speed = 1;
+        public static float Speed { get; set; } = 1;
         
         public static Color Color { get; private set; } = Color.Blue;
 
+        private static float _lastHue;
+
         public static void Tick()
         {
+            float currentHue = Color.GetHue();
+            float nextHue = currentHue;
+
+            if (currentHue >= 360)
+                nextHue = 0;
+            else
+                nextHue += Speed;
+            
             Color = HsbToRgb(
-                (Color.GetHue() + Speed) / 360,
+                nextHue / 360,
                 1, 
                 1
                 );
+
+            _lastHue = currentHue;
             
             RainbowColorUpdated?.Invoke(Color.ToArgb());
         }