1465 Integration tests for cloud_firestore and firebase_database transactions (cla: yes, flutterfire)

1466 [cloud_firestore]remove white spaces. (cla: yes)

1467 [cloud_firestore]remove blank line. (cla: yes)

1468 Migrate firebase messaging plugin away from token (cla: yes)

1470 [video_player] Android: Added missing event.put(“event”, “completed”); (bugfix, cla: yes)

1471 [image_picker] Fix invalid path being returned from Google Photos (bugfix, cla: yes)

1472 [Google_map]Enable iOS a11y by default. (cla: yes)

1473 [package_info] Integration tests. (cla: yes)