refactor: move xmodule folder to root

- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
    - More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore

openedx/core/djangoapps/content/learning_sequences/api/processors/enrollment_track_partition_groups.py

@@ -44,7 +44,8 @@ class EnrollmentTrackPartitionGroupsOutlineProcessor(OutlineProcessor):
             self.user,
             partition_dict_key='id'
         )
-        self.user_group = self.enrollment_track_groups.get(ENROLLMENT_TRACK_PARTITION_ID)
+        # TODO: fix type annotation: https://github.com/openedx/tcril-engineering/issues/313
+        self.user_group = self.enrollment_track_groups.get(ENROLLMENT_TRACK_PARTITION_ID)  # type: ignore
 
     def _is_user_excluded_by_partition_group(self, user_partition_groups):
         """

openedx/core/djangoapps/discussions/tests/test_tasks.py

@@ -4,12 +4,13 @@ Tests for discussions tasks.
 import ddt
 import mock
 
-from xmodule.modulestore.tests.django_utils import TEST_DATA_MONGO_AMNESTY_MODULESTORE, ModuleStoreTestCase
-from xmodule.modulestore.tests.factories import CourseFactory, ItemFactory
 
 from openedx_events.learning.data import DiscussionTopicContext
 from openedx.core.djangoapps.discussions.tasks import update_discussions_settings_from_course
 
+from xmodule.modulestore.tests.django_utils import TEST_DATA_MONGO_AMNESTY_MODULESTORE, ModuleStoreTestCase
+from xmodule.modulestore.tests.factories import CourseFactory, ItemFactory
+
 
 @ddt.ddt
 @mock.patch('openedx.core.djangoapps.discussions.tasks.DiscussionsConfiguration', mock.Mock())

openedx/core/djangoapps/xblock/runtime/shims.py

@@ -90,7 +90,7 @@ class RuntimeShim:
     def can_execute_unsafe_code(self):
         """
         Determine if capa problems in this context/course are allowed to run
-        unsafe code. See common/lib/xmodule/xmodule/util/sandboxing.py
+        unsafe code. See xmodule/util/sandboxing.py
 
         Seems only to be used by capa.
         """