Misc performance tweaks (#4509)

* use Array.Empty() where instead of allocating new zero-length arrays

* structure for loops in a way that the JIT will elide array/Span bounds checking

* avoiding function calls in for loop condition tests

* avoid LINQ in a hot path

* conform with code style

* fix mistake in GetNextWaitingObject()

* fix GetNextWaitingObject() possibility of returning null if all list items have TimePoint == long.MaxValue

* make GetNextWaitingObject() behave FIFO behavior for multiple items with the same TimePoint

Ryujinx.Ava/UI/Windows/IconColorPicker.cs

@@ -125,7 +125,7 @@ namespace Ryujinx.Ava.UI.Windows
 
         public static Bgra32[] GetBuffer(Image<Bgra32> image)
         {
-            return image.TryGetSinglePixelSpan(out var data) ? data.ToArray() : new Bgra32[0];
+            return image.TryGetSinglePixelSpan(out var data) ? data.ToArray() : Array.Empty<Bgra32>();
         }
 
         private static int GetColorScore(Dictionary<int, int> dominantColorBin, int maxHitCount, PaletteColor color)