CmdPal: Set image to surface immediately in BlurImageControl (#44222)

## Summary of the Pull Request

This PR resolves issue when the background image is not loaded. When
loading an image, BlurImageControl now sets the image to the surface
immediately, as the LoadComplete handler is not guaranteed to be called.

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## PR Checklist

- [x] Closes: #44221
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issues) -->
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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

Author: jiripolasek

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/BlurImageControl.cs

@@ -368,32 +368,69 @@ private void LoadImageAsync(ImageSource imageSource)
     {
         try
         {
-            if (imageSource is Microsoft.UI.Xaml.Media.Imaging.BitmapImage bitmapImage)
+            if (imageSource is not Microsoft.UI.Xaml.Media.Imaging.BitmapImage bitmapImage)
             {
-                _imageBrush ??= _compositor?.CreateSurfaceBrush();
-                if (_imageBrush is null)
-                {
-                    return;
-                }
-
-                var loadedSurface = LoadedImageSurface.StartLoadFromUri(bitmapImage.UriSource);
-                loadedSurface.LoadCompleted += (_, _) =>
-                {
-                    if (_imageBrush is not null)
-                    {
-                        _imageBrush.Surface = loadedSurface;
-                        _imageBrush.Stretch = ConvertStretch(ImageStretch);
-                        _imageBrush.BitmapInterpolationMode = CompositionBitmapInterpolationMode.Linear;
-                    }
-                };
+                return;
+            }
 
-                _effectBrush?.SetSourceParameter(ImageSourceParameterName, _imageBrush);
+            _imageBrush ??= _compositor?.CreateSurfaceBrush();
+            if (_imageBrush is null)
+            {
+                return;
             }
+
+            Logger.LogDebug($"Starting load of BlurImageControl from '{bitmapImage.UriSource}'");
+            var loadedSurface = LoadedImageSurface.StartLoadFromUri(bitmapImage.UriSource);
+            loadedSurface.LoadCompleted += OnLoadedSurfaceOnLoadCompleted;
+            SetLoadedSurfaceToBrush(loadedSurface);
+            _effectBrush?.SetSourceParameter(ImageSourceParameterName, _imageBrush);
         }
         catch (Exception ex)
         {
             Logger.LogError("Failed to load image for BlurImageControl: {0}", ex);
         }
+
+        return;
+
+        void OnLoadedSurfaceOnLoadCompleted(LoadedImageSurface loadedSurface, LoadedImageSourceLoadCompletedEventArgs e)
+        {
+            switch (e.Status)
+            {
+                case LoadedImageSourceLoadStatus.Success:
+                    Logger.LogDebug($"BlurImageControl loaded successfully: has _imageBrush? {_imageBrush != null}");
+
+                    try
+                    {
+                        SetLoadedSurfaceToBrush(loadedSurface);
+                    }
+                    catch (Exception ex)
+                    {
+                        Logger.LogError("Failed to set surface in BlurImageControl", ex);
+                        throw;
+                    }
+
+                    break;
+                case LoadedImageSourceLoadStatus.NetworkError:
+                case LoadedImageSourceLoadStatus.InvalidFormat:
+                case LoadedImageSourceLoadStatus.Other:
+                default:
+                    Logger.LogError($"Failed to load image for BlurImageControl: Load status {e.Status}");
+                    break;
+            }
+        }
+    }
+
+    private void SetLoadedSurfaceToBrush(LoadedImageSurface loadedSurface)
+    {
+        var surfaceBrush = _imageBrush;
+        if (surfaceBrush is null)
+        {
+            return;
+        }
+
+        surfaceBrush.Surface = loadedSurface;
+        surfaceBrush.Stretch = ConvertStretch(ImageStretch);
+        surfaceBrush.BitmapInterpolationMode = CompositionBitmapInterpolationMode.Linear;
     }
 
     private static CompositionStretch ConvertStretch(Stretch stretch)