feat!: drop legacy course home view and related code

This was the "outline tab" view of the course. Preceded by the
course info view, succeeded by the MFE outline tab.

In addition to the course home view itself, this drops related
features:
- Legacy version of Course Goals (MFE has a newer implementation)
- Course home in-course search (MFE has no search)

The old course info view and course about views survive for now.

This also drops a few now-unused feature toggles:
- course_experience.latest_update
- course_experience.show_upgrade_msg_on_course_home
- course_experience.upgrade_deadline_message
- course_home.course_home_use_legacy_frontend

With this change, just the progress and courseware tabs are still
supported in legacy form, if you opt-in with waffle flags. The
outline and dates tabs are offered only by the MFE.

AA-798

(This is identical to previous commit be5c1a6, just reintroduced
now that the e2e tests have been fixed)

common/djangoapps/course_modes/tests/test_views.py

@@ -104,10 +104,8 @@ class CourseModeViewTest(CatalogIntegrationMixin, UrlResetMixin, ModuleStoreTest
         # Check whether we were correctly redirected
         if redirect:
             if has_started:
-                self.assertRedirects(
-                    response, reverse('openedx.course_experience.course_home', kwargs={'course_id': course.id}),
-                    target_status_code=302,  # for follow-on redirection to MFE (ideally we'd just be sent there first)
-                )
+                mfe_url = f'http://learning-mfe/course/{course.id}/home'
+                self.assertRedirects(response, mfe_url, fetch_redirect_response=False)
             else:
                 self.assertRedirects(response, reverse('dashboard'))
         else: