Use ColdPath for Block8x8F

Author: JimBobSquarePants

src/ImageSharp/Formats/Jpeg/Components/Block8x8F.ScaledCopy.cs

@@ -14,7 +14,7 @@ internal partial struct Block8x8F
     public void ScaledCopyFrom(ref float areaOrigin, int areaStride) =>
         CopyFrom1x1Scale(ref Unsafe.As<float, byte>(ref areaOrigin), ref Unsafe.As<Block8x8F, byte>(ref this), areaStride);
 
-    [MethodImpl(InliningOptions.ShortMethod)]
+    [MethodImpl(InliningOptions.ColdPath)]
     public void ScaledCopyTo(ref float areaOrigin, int areaStride, int horizontalScale, int verticalScale)
     {
         if (horizontalScale == 1 && verticalScale == 1)

src/ImageSharp/Formats/Jpeg/Components/Decoder/ComponentProcessors/DownScalingComponentProcessor8.cs

@@ -111,6 +111,14 @@ public static void ScaledCopyTo(float value, ref float destRef, int destStrideWi
             return;
         }
 
+        // The common 1x, 2x, and 4x integral scales are specialized above.
+        // Uncommon legal factor-3 scales use the generic fallback.
+        CopyArbitraryScale(value, ref destRef, destStrideWidth, horizontalScale, verticalScale);
+    }
+
+    [MethodImpl(InliningOptions.ColdPath)]
+    private static float CopyArbitraryScale(float value, ref float destRef, int destStrideWidth, int horizontalScale, int verticalScale)
+    {
         // The common 1x, 2x, and 4x integral scales are specialized above.
         // Uncommon legal factor-3 scales use the generic fallback.
         for (nuint y = 0; y < (uint)verticalScale; y++)
@@ -122,6 +130,8 @@ public static void ScaledCopyTo(float value, ref float destRef, int destStrideWi
 
             destRef = ref Unsafe.Add(ref destRef, (uint)destStrideWidth);
         }
+
+        return destRef;
     }
 
     /// <summary>