android notif [nfc]: Remove InstanceIDListenerService.java.

This is deprecated [1][2] in favor of overriding
`FirebaseMessagingService#onNewToken`.

While not causing any noticable bugs, its good to have up to date
code. One benefit of this specific commit is that it removes some
code.

Something related but not done in this commit is to update
firebase-messaging itself, which as of now stands at 22.0.0 .

[1] https://firebase.google.com/docs/reference/android/com/google/firebase/iid/FirebaseInstanceIdService
[2] https://firebase.google.com/support/release-notes/android#firebase_instance_id_version_1620

Author: AkashDhiman

android/app/src/main/AndroidManifest.xml

@@ -87,13 +87,5 @@
                 <action android:name="com.google.firebase.MESSAGING_EVENT" />
             </intent-filter>
         </service>
-
-        <service
-            android:name=".notifications.InstanceIDListenerService"
-            android:exported="false">
-            <intent-filter>
-                <action android:name="com.google.firebase.INSTANCE_ID_EVENT" />
-            </intent-filter>
-        </service>
     </application>
 </manifest>

android/app/src/main/java/com/zulipmobile/notifications/FcmListenerService.java

@@ -1,6 +1,8 @@
 package com.zulipmobile.notifications;
 
 import android.content.Context;
+import com.facebook.react.ReactApplication;
+import com.facebook.react.bridge.ReactContext;
 import com.google.firebase.messaging.FirebaseMessagingService;
 import com.google.firebase.messaging.RemoteMessage;
 
@@ -17,4 +19,15 @@ public void onMessageReceived(RemoteMessage message) {
                 ((MainApplication) applicationContext).getConversations();
         FCMPushNotifications.onReceived(this, conversations, message.getData());
     }
+
+    @Override
+    public void onNewToken(String token) {
+        super.onNewToken(token);
+        final ReactContext reactContext =
+                ((ReactApplication) getApplication())
+                        .getReactNativeHost()
+                        .getReactInstanceManager()
+                        .getCurrentReactContext();
+        NotificationsModule.emitToken(reactContext, token);
+    }
 }

android/app/src/main/java/com/zulipmobile/notifications/InstanceIDListenerService.java

@@ -21,8 +21,7 @@ public String getName() {
         return "Notifications";
     }
 
-    static void emitToken(@Nullable ReactContext reactContext) {
-        final String token = FirebaseInstanceId.getInstance().getToken();
+    static void emitToken(@Nullable ReactContext reactContext, String token) {
         if (reactContext == null) {
             // Perhaps this is possible if InstanceIDListenerService gets invoked?
             return;