Certificate Display Settings revamp (round 2) (#28286)

feat: reimagine certificate display settings

The course settings `certificate_available_date` (CAD) and
`certificates_display_behavior` (CDB) were previously
acting indedependantly of one another. They now work in
tandem. This change:
- limits CDB to a dropdown
- removes "early_with_info" and adds "end_with_date"
- only takes CAD into account if "end_with_date" is selected
- Moves CDB to the main course schedule settings page
- updates CourseOverview model and CourseDetails objects to
validate these fields and choose sane defaults if they aren't
expected values

This work was previously done in bd9e7dd (complete with bugs), so this
version is toggleable via the ENABLE_V2_CERT_DISPLAY_SETTINGS setting

openedx/features/learner_profile/tests/views/test_learner_profile.py

@@ -21,6 +21,7 @@ from openedx.core.djangoapps.content.course_overviews.models import CourseOvervi
 from openedx.core.djangoapps.site_configuration.tests.mixins import SiteMixin
 from openedx.features.learner_profile.toggles import REDIRECT_TO_PROFILE_MICROFRONTEND
 from openedx.features.learner_profile.views.learner_profile import learner_profile_context
+from xmodule.data import CertificatesDisplayBehaviors
 from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
 from xmodule.modulestore.tests.factories import CourseFactory
 
@@ -222,7 +223,8 @@ class LearnerProfileViewTest(SiteMixin, UrlResetMixin, ModuleStoreTestCase):
         """
         # add new course with certificate_available_date is future date.
         course = CourseFactory.create(
-            certificate_available_date=datetime.datetime.now() + datetime.timedelta(days=5)
+            certificate_available_date=datetime.datetime.now() + datetime.timedelta(days=5),
+            certificates_display_behavior=CertificatesDisplayBehaviors.END_WITH_DATE
         )
 
         cert = self._create_certificate(course_key=course.id)