fix(macos): Use case-insensitive API to load images from bundle

- also remove dead/unused method, unused since c0d16ea

Addresses #8666

Author: spouliot

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

@@ -62,12 +62,11 @@ public bool HasSource()
 		public bool HasBundle => BundlePath.HasValueTrimmed() || BundleName.HasValueTrimmed();
 
 		/// <summary>
-		/// Open bundle is using either the name of the bundle (for 
-		/// android compatibility), or the path to the bundle for Windows compatibility.
+		/// Open the image from the app's main bundle.
 		/// </summary>
 		internal NSImage OpenBundle()
 		{
-			ImageData = OpenBundleFromString(BundleName) ?? OpenResourceFromString(BundlePath);
+			ImageData = OpenResourceFromString(BundlePath) ?? OpenResourceFromString(BundleName);
 
 			if (ImageData == null)
 			{
@@ -77,28 +76,13 @@ internal NSImage OpenBundle()
 			return ImageData;
 		}
 
-		private static NSImage OpenBundleFromString(string bundle)
-		{
-			if (bundle.HasValueTrimmed())
-			{
-				return NSImage.ImageNamed(bundle);
-			}
-
-			return null;
-		}
-
 		private static NSImage OpenResourceFromString(string name)
 		{
 			if (name.HasValueTrimmed())
 			{
-				var extension = Path.GetExtension(name);
-				var fileName = name.Replace(extension, string.Empty);
-
-				var path = NSBundle.MainBundle.PathForResource(fileName, extension);
-
-				return !string.IsNullOrEmpty(path)
-								? new NSImage(path)
-								: null;
+				var path = Path.Combine(NSBundle.MainBundle.ResourcePath, name);
+				if (File.Exists(path))
+					return new NSImage(path);
 			}
 
 			return null;