Add custom refresh rate mode to VSync option (#238)

Rebased @jcm93's refreshinterval branch:
https://github.com/jcm93/Ryujinx/tree/refreshinterval

The option is placed under System/Hacks. Disabled, it's the default
Ryujinx behavior. Enabled, the behavior is shown in the attached
screenshots. If a framerate is too high or low, you can adjust the value
where you normally toggle VSync on and off. It will also cycle through
the default on/off toggles.

Also, in order to reduce clutter, I made an adjustment to remove the
target FPS and only show the percentage.

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Co-authored-by: jcm <6864788+jcm93@users.noreply.github.com>

src/Ryujinx.Graphics.Vulkan/WindowBase.cs

@@ -10,7 +10,7 @@ namespace Ryujinx.Graphics.Vulkan
         public abstract void Dispose();
         public abstract void Present(ITexture texture, ImageCrop crop, Action swapBuffersCallback);
         public abstract void SetSize(int width, int height);
-        public abstract void ChangeVSyncMode(bool vsyncEnabled);
+        public abstract void ChangeVSyncMode(VSyncMode vSyncMode);
         public abstract void SetAntiAliasing(AntiAliasing effect);
         public abstract void SetScalingFilter(ScalingFilter scalerType);
         public abstract void SetScalingFilterLevel(float scale);