FCM - Notification Image not displaying

### Describe your environment

* Operating System version: macOS 13.0 (22A380)
* Firebase SDK version: 9.1.1
* Library version: 9.1.1
* Firebase Product: Cloud Messaging (auth, database, storage, etc)

#### Steps to reproduce:

Images are not displayed on devices (both iOS and Android) when sending notifications with FCM.
I set the image URL using the Notification Builder.

```
List fcmTokens = List.of(...);

Notification notification = Notification.builder().setTitle("Hello").setBody("world").setImage("https://e-cdns-images.dzcdn.net/images/cover/f2d3db07f3f045a048cdacf53b5cf9dd/250x250-000000-80-0-0.jpg").build();

MulticastMessage message = MulticastMessage.builder()
.setNotification(notification)
.addAllTokens(fcmTokens).build();

BatchResponse response = FirebaseMessaging.getInstance().sendMulticast(message);
```

Note that I receive the notification on the devices, only the image is not displayed. I am able to see the image in the notification when sending it using the Firebase Console.

When investigating the issue, I discovered that other SDKs use `imageUrl` instead of `image` attribute.
For example, for NodeJS: https://firebase.google.com/docs/reference/admin/node/firebase-admin.messaging.notification.md#notificationimageurl

The Java SDK still uses the `image` key instead of `imageUrl`: https://github.com/firebase/firebase-admin-java/blob/master/src/main/java/com/google/firebase/messaging/Notification.java#L33

Commencez par le fichier référencé src/main/java/com/google/firebase/messaging/Notification.java et comparez son champ image avec la référence imageUrl liée de Node.js. Suivez la représentation de Notification dans la requête FCM, puis validez l’exemple multicast fourni sur iOS et Android ; le travail est terminé lorsque l’image de la notification s’affiche.

Rédigé par le modèle d'indexation à partir du texte de l'issue.