Use the scale category from `NSImage+Addtions` instead of manual created property for `SDAnimatedImage` on macOS

SDWebImage/SDAnimatedImage.h

@@ -78,7 +78,7 @@
  The scale factor of the image.
  
  @note For UIKit, this just call super instead.
- @note For AppKit, `NSImage` can contains multiple image representations with different scales. However, this class does not do that from the design. We processs the scale like UIKit and store it as a extra information for correctlly rendering in `SDAnimatedImageView`.
+ @note For AppKit, `NSImage` can contains multiple image representations with different scales. However, this class does not do that from the design. We processs the scale like UIKit. This wil actually be calculated from image size and pixel size.
  */
 @property (nonatomic, readonly) CGFloat scale;
 

SDWebImage/SDAnimatedImage.m

@@ -205,9 +205,7 @@ static NSArray *SDBundlePreferredScales() {
 @end
 
 @implementation SDAnimatedImage
-#if SD_UIKIT || SD_WATCH
 @dynamic scale; // call super
-#endif
 
 #pragma mark - UIImage override method
 + (instancetype)imageNamed:(NSString *)name {
@@ -316,9 +314,6 @@ static NSArray *SDBundlePreferredScales() {
 #endif
     if (self) {
         _coder = animatedCoder;
-#if SD_MAC
-        _scale = scale;
-#endif
         NSData *data = [animatedCoder animatedImageData];
         SDImageFormat format = [NSData sd_imageFormatForImageData:data];
         _animatedImageFormat = format;
@@ -353,17 +348,7 @@ static NSArray *SDBundlePreferredScales() {
     self = [super initWithCoder:aDecoder];
     if (self) {
         NSData *animatedImageData = [aDecoder decodeObjectOfClass:[NSData class] forKey:NSStringFromSelector(@selector(animatedImageData))];
-        CGFloat scale;
-#if SD_MAC
-        NSNumber *scaleValue = [aDecoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(scale))];
-        scale = scaleValue.doubleValue;
-        if (scale < 1) {
-            scale = 1;
-        }
-        _scale = scale;
-#else
-        scale = self.scale;
-#endif
+        CGFloat scale = self.scale;
         if (!animatedImageData) {
             return self;
         }
@@ -388,9 +373,6 @@ static NSArray *SDBundlePreferredScales() {
 
 - (void)encodeWithCoder:(NSCoder *)aCoder {
     [super encodeWithCoder:aCoder];
-#if SD_MAC
-    [aCoder encodeObject:@(self.scale) forKey:NSStringFromSelector(@selector(scale))];
-#endif
     NSData *animatedImageData = self.animatedImageData;
     if (animatedImageData) {
         [aCoder encodeObject:animatedImageData forKey:NSStringFromSelector(@selector(animatedImageData))];

SDWebImage/SDWebImageGIFCoder.m

@@ -99,7 +99,7 @@
     
     BOOL decodeFirstFrame = [options[SDWebImageCoderDecodeFirstFrameOnly] boolValue];
     if (decodeFirstFrame || count <= 1) {
-        animatedImage = [[UIImage alloc] initWithData:data];
+        animatedImage = [[UIImage alloc] initWithData:data scale:scale];
     } else {
         NSMutableArray<SDWebImageFrame *> *frames = [NSMutableArray array];