Fix Image defaultSource not showing on iOS (#32172)

Summary:
Fix Image defaultSource not showing on iOS.

This bug was introduced somewhere between RN 0.63 and 0.65. On iOS, defaultSource does not show while the image is being downloaded, only if it fails or there's no internet.

## Changelog

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[iOS] [Fixed] - Fix Image defaultSource not showing on iOS

Pull Request resolved: #32172

Test Plan: Ran both debug and release builds on an iPhone 12 pro (iOS 14.6)

Reviewed By: sammy-SC

Differential Revision: D30822805

Pulled By: lunaleaps

fbshipit-source-id: c4ef18723a8311ef3be1d7ae25ff3c205e8fff62

Author: cristianoccazinsp

Libraries/Image/RCTImageView.mm

@@ -234,6 +234,10 @@ - (void)cancelAndClearImageLoad
 
   [_imageLoader trackURLImageRequestDidDestroy:_loaderRequest];
   _loaderRequest = nil;
+  
+  if (!self.image) {
+    self.image = _defaultImage;
+  }
 }
 
 - (void)clearImageIfDetached

packages/rn-tester/js/examples/Image/ImageExample.js

@@ -585,7 +585,7 @@ class OnPartialLoadExample extends React.Component<
   }
 }
 
-const fullImage = {
+const fullImage: ImageSource = {
   uri: 'https://www.facebook.com/ads/pics/successstories.png',
 };
 const smallImage = {
@@ -747,7 +747,9 @@ exports.examples = [
         <Image
           defaultSource={require('../../assets/bunny.png')}
           source={{
-            uri: 'https://origami.design/public/images/bird-logo.png',
+            // Note: Use a large image and bust cache so we can in fact
+            // visualize the `defaultSource` image.
+            uri: fullImage.uri + '?cacheBust=notinCache' + Date.now(),
           }}
           style={styles.base}
         />