Add icon for in-app feedback notifications (#4320)

Author: lfkellogg

firebase-appdistribution/src/main/java/com/google/firebase/appdistribution/impl/FirebaseAppDistributionNotificationsManager.java

@@ -159,7 +159,7 @@ public void showFeedbackNotification(
     CharSequence appLabel = packageManager.getApplicationLabel(applicationInfo);
     NotificationCompat.Builder builder =
         new NotificationCompat.Builder(context, Notification.FEEDBACK.channelId)
-            .setSmallIcon(appIconSource.getNonAdaptiveIconOrDefault(context))
+            .setSmallIcon(R.drawable.ic_baseline_rate_review_24)
             .setContentTitle(context.getString(R.string.feedback_notification_title))
             .setContentText(context.getString(R.string.feedback_notification_text, appLabel))
             .setPriority(interruptionLevel.notificationPriority)

firebase-appdistribution/src/main/res/drawable/ic_baseline_rate_review_24.xml

@@ -0,0 +1,5 @@
+<vector android:height="24dp" android:tint="#000000"
+    android:viewportHeight="24" android:viewportWidth="24"
+    android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="@android:color/white" android:pathData="M20,2L4,2c-1.1,0 -1.99,0.9 -1.99,2L2,22l4,-4h14c1.1,0 2,-0.9 2,-2L22,4c0,-1.1 -0.9,-2 -2,-2zM6,14v-2.47l6.88,-6.88c0.2,-0.2 0.51,-0.2 0.71,0l1.77,1.77c0.2,0.2 0.2,0.51 0,0.71L8.47,14L6,14zM18,14h-7.5l2,-2L18,12v2z"/>
+</vector>