Move request_cache to openedx.core.djangoapps

cms/djangoapps/contentstore/config/tests/utils.py

cms/djangoapps/xblock_config/models.py

cms/djangoapps/xblock_config/tests/test_models.py

cms/envs/common.py

common/djangoapps/course_modes/models.py

common/djangoapps/django_comment_common/utils.py

common/djangoapps/edxmako/paths.py

common/djangoapps/edxmako/request_context.py

common/djangoapps/edxmako/tests.py

common/djangoapps/student/models.py

common/djangoapps/student/roles.py

common/djangoapps/track/event_transaction_utils.py

common/djangoapps/util/db.py

common/djangoapps/util/milestones_helpers.py

common/lib/xmodule/xmodule/modulestore/django.py

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

lms/djangoapps/ccx/overrides.py

lms/djangoapps/ccx/tests/test_field_override_performance.py

lms/djangoapps/ccx/tests/test_overrides.py

lms/djangoapps/ccx/tests/test_views.py