refactor: deprecate ModuleSystem user attributes in favor of user service

The following ModuleSystem attributes are deprecated by this change, and should be pulled directly from the user service instead:

* anonymous_student_id
* seed
* user_id
* user_is_staff

Related changes:

* Removes the `user` and `anonymous_student_id` parameters from the ModuleService constructor.
* Stores anonymous_user_id in XBlockDjangoUserService's opt_attr
* Pulls out constants used by DjangoXBlockUserService opt_attr so they can be used in the platform code.
* LmsModuleSystem uses the user service created in wrapper function for runtime.publish to avoid requiring the user
  service to be "needed" by all XBlocks.
* LmsModuleSystem no longer checks for instances of XModuleDescriptor when deciding what kind of anonymous_user_id to
  provide:  all XModules are XBlocks, so this check is unnecessary.
* XBlockRuntime returns a user service when requested
* Adds tests for deprecated ModuleSystem attributes and changes to XBlockDjangoUserService.

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

@@ -21,6 +21,7 @@ from xblock.runtime import KvsFieldData, MemoryIdManager, Runtime
 
 from common.djangoapps.track import contexts as track_contexts
 from common.djangoapps.track import views as track_views
+from common.djangoapps.xblock_django.user_service import DjangoXBlockUserService
 from lms.djangoapps.courseware.model_data import DjangoKeyValueStore, FieldDataCache
 from lms.djangoapps.grades.api import signals as grades_signals
 from openedx.core.djangoapps.xblock.apps import get_xblock_app_config
@@ -226,6 +227,14 @@ class XBlockRuntime(RuntimeShim, Runtime):
         elif service_name == "completion":
             context_key = block.scope_ids.usage_id.context_key
             return CompletionService(user=self.user, context_key=context_key)
+        elif service_name == "user":
+            return DjangoXBlockUserService(
+                self.user,
+                # The value should be updated to whether the user is staff in the context when Blockstore runtime adds
+                # support for courses.
+                user_is_staff=self.user.is_staff,
+                anonymous_user_id=self.anonymous_student_id,
+            )
         elif service_name == "i18n":
             return ModuleI18nService(block=block)
         # Check if the XBlockRuntimeSystem wants to handle this: