fix: Raise ImageFailed properly on Android

src/Uno.UI/UI/Xaml/Controls/Image/Image.Android.cs

@@ -146,6 +146,13 @@ namespace Windows.UI.Xaml.Controls
 				}
 			}
 
+			if (imageSource.ResourceFailed)
+			{
+				// Currently resource-based images are evaluated immediately
+				// in the constructor - so we have to raise ImageFailed late.				
+				OnImageFailed(imageSource, new InvalidOperationException("Resource could not be found"));
+			}
+
 			if (this.Log().IsEnabled(Uno.Foundation.Logging.LogLevel.Debug))
 			{
 				this.Log().Debug(this.ToString() + " TryOpenImage - proceeding");

src/Uno.UI/UI/Xaml/Media/ImageSource.Android.cs

@@ -91,6 +91,8 @@ namespace Windows.UI.Xaml.Media
 				|| ResourceId != null;
 		}
 
+		internal bool ResourceFailed => ResourceString is not null && ResourceId is null;
+
 		internal BitmapDrawable? BitmapDrawable { get; private set; }
 
 		internal int? ResourceId