feat: Update new files notification banner styles (#33197)

Uses the updated styles for the notification based on the new designs.
Includes a button to open view the files directly in the notification.

This also fix a bug where the notification was not appearing when paste
a whole Unit.

cms/djangoapps/contentstore/tests/test_contentstore.py

@@ -1406,11 +1406,16 @@ class ContentStoreTest(ContentStoreTestCase):
             self.assertEqual(resp.status_code, 404)
             return
 
+        assets_url = reverse_course_url(
+            'assets_handler',
+            course.location.course_key
+        )
         self.assertContains(
             resp,
-            '<article class="outline outline-complex outline-course" data-locator="{locator}" data-course-key="{course_key}">'.format(  # lint-amnesty, pylint: disable=line-too-long
+            '<article class="outline outline-complex outline-course" data-locator="{locator}" data-course-key="{course_key}" data-course-assets="{assets_url}">'.format(  # lint-amnesty, pylint: disable=line-too-long
                 locator=str(course.location),
                 course_key=str(course.id),
+                assets_url=assets_url,
             ),
             status_code=200,
             html=True