refactor!: switch from LegacyWaffle* to modern waffles (#30330)

This is a first stage for removing the LegacyWaffle* classes.

LegacyWaffleFlag usage replaced with WaffleFlag;
LegacyWaffleSwitche usage replaced with WaffleSwitch;
New CourseWaffleFlag added to the temporary module __future__ as FutureCourseWaffleFlag;
Updated all the imports to use CourseWaffleFlag from the __future__ module;

BREAKING CHANGE: A number of toggle related constants (e.g. ENABLE_ACCESSIBILITY_POLICY_PAGE)
changed types. They were strings, and are now toggle instances (e.g. WaffleSwitch). Although the entire
refactor should be self-contained in edx-platform, if any plugins or dependencies were directly
using these constants, they will break. If this is the case, try to find a better publicized way of
exposing those toggles.

common/djangoapps/student/views/dashboard.py

@@ -16,7 +16,7 @@ from django.utils.translation import gettext as _
 from django.views.decorators.csrf import ensure_csrf_cookie
 from edx_django_utils import monitoring as monitoring_utils
 from edx_django_utils.plugins import get_plugins_view_context
-from edx_toggles.toggles import LegacyWaffleFlag, LegacyWaffleFlagNamespace
+from edx_toggles.toggles import WaffleFlag
 from opaque_keys.edx.keys import CourseKey
 from pytz import UTC
 
@@ -61,7 +61,7 @@ from xmodule.modulestore.django import modulestore  # lint-amnesty, pylint: disa
 
 log = logging.getLogger("edx.student")
 
-experiments_namespace = LegacyWaffleFlagNamespace(name='student.experiments')
+EXPERIMENTS_NAMESPACE = 'student.experiments'
 
 
 def get_org_black_and_whitelist_for_site():
@@ -652,7 +652,7 @@ def student_dashboard(request):  # lint-amnesty, pylint: disable=too-many-statem
     inverted_programs = meter.invert_programs()
 
     urls, programs_data = {}, {}
-    bundles_on_dashboard_flag = LegacyWaffleFlag(experiments_namespace, 'bundles_on_dashboard', __name__)  # lint-amnesty, pylint: disable=toggle-missing-annotation
+    bundles_on_dashboard_flag = WaffleFlag(f'{EXPERIMENTS_NAMESPACE}.bundles_on_dashboard', __name__)  # lint-amnesty, pylint: disable=toggle-missing-annotation
 
     # TODO: Delete this code and the relevant HTML code after testing LEARNER-3072 is complete
     if bundles_on_dashboard_flag.is_enabled() and inverted_programs and list(inverted_programs.items()):

common/lib/xmodule/xmodule/seq_module.py

@@ -22,7 +22,7 @@ from xblock.core import XBlock
 from xblock.exceptions import NoSuchServiceError
 from xblock.fields import Boolean, Integer, List, Scope, String
 
-from edx_toggles.toggles import LegacyWaffleFlag, SettingDictToggle
+from edx_toggles.toggles import WaffleFlag, SettingDictToggle
 from xmodule.util.xmodule_django import add_webpack_to_fragment
 from xmodule.x_module import (
     HTMLSnippet,
@@ -58,10 +58,8 @@ class_priority = ['video', 'problem']
 #  `django.utils.translation.ugettext_noop` because Django cannot be imported in this file
 _ = lambda text: text
 
-TIMED_EXAM_GATING_WAFFLE_FLAG = LegacyWaffleFlag(  # lint-amnesty, pylint: disable=toggle-missing-annotation
-    waffle_namespace="xmodule",
-    flag_name='rev_1377_rollout',
-    module_name=__name__,
+TIMED_EXAM_GATING_WAFFLE_FLAG = WaffleFlag(  # lint-amnesty, pylint: disable=toggle-missing-annotation
+    'xmodule.rev_1377_rollout', __name__
 )
 
 # .. toggle_name: FEATURES['SHOW_PROGRESS_BAR']

common/lib/xmodule/xmodule/video_module/video_module.py

@@ -31,7 +31,7 @@ from xblock.runtime import KvsFieldData
 
 from common.djangoapps.xblock_django.constants import ATTR_KEY_REQUEST_COUNTRY_CODE
 from openedx.core.djangoapps.video_config.models import HLSPlaybackEnabledFlag, CourseYoutubeBlockedFlag
-from openedx.core.djangoapps.video_pipeline.config.waffle import DEPRECATE_YOUTUBE, waffle_flags
+from openedx.core.djangoapps.video_pipeline.config.waffle import DEPRECATE_YOUTUBE
 from openedx.core.lib.cache_utils import request_cached
 from openedx.core.lib.license import LicenseMixin
 from xmodule.contentstore.content import StaticContent
@@ -198,7 +198,7 @@ class VideoBlock(
 
         # check if youtube has been deprecated and hls as primary playback
         # is enabled for this course
-        return waffle_flags()[DEPRECATE_YOUTUBE].is_enabled(self.location.course_key)
+        return DEPRECATE_YOUTUBE.is_enabled(self.location.course_key)
 
     def youtube_disabled_for_course(self):  # lint-amnesty, pylint: disable=missing-function-docstring
         if not self.location.context_key.is_course: