Add option to export images in "assetName@hash" name format

- Redesigned spriteHelper & texture2DConverter
- Improved speed of texture2D preview a bit

AssetStudioUtility/SpriteExtensions.cs

@@ -0,0 +1,13 @@
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace AssetStudio
+{
+    public static class SpriteExtensions
+    {
+        public static bool TryGetImage(this Sprite m_Sprite, out Image<Bgra32> spriteImage, SpriteMaskMode spriteMaskMode = SpriteMaskMode.On)
+        {
+            return new SpriteConverter(m_Sprite).TryConvertToImage(out spriteImage, spriteMaskMode);
+        }
+    }
+}