fix(iOS): release previous UIImage on source prop change to prevent memory leak

When the Image component's source prop changes, the UIImageView retains
the previous UIImage until the new image loads. On rapid source changes
(e.g., image carousels, animations), this causes memory accumulation
since old images are not released promptly.

Explicitly setting _imageView.image = nil in
_setStateAndResubscribeImageResponseObserver: ensures the previous
UIImage is released when the state (and thus source) changes,
preventing unbounded memory growth.

Fixes #12220

Author: MuhammadSuleman97

packages/react-native/React/Fabric/Mounting/ComponentViews/Image/RCTImageComponentView.mm

@@ -140,6 +140,12 @@ - (void)_setStateAndResubscribeImageResponseObserver:(const ImageShadowNode::Con
     observerCoordinator.removeObserver(_imageResponseObserverProxy);
   }
 
+  // Release the previous image to prevent memory accumulation
+  // when the source prop changes rapidly (e.g., in animations/slideshows).
+  // The UIImageView retains the UIImage, preventing deallocation until
+  // the next image arrives, which can cause significant memory growth.
+  _imageView.image = nil;
+
   _state = state;
 
   if (_state) {
@@ -301,4 +307,4 @@ - (void)didReceiveFailure:(NSError *)error fromObserver:(const void *)observer
 Class<RCTComponentViewProtocol> RCTImageCls(void)
 {
   return RCTImageComponentView.class;
-}
+}