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.

(cherry picked from commit c41e7fb93a)

cms/djangoapps/contentstore/views/preview.py

@@ -198,12 +198,10 @@ def _preview_module_system(request, descriptor, field_data):
         render_template=render_from_lms,
         debug=True,
         replace_urls=partial(static_replace.replace_static_urls, data_directory=None, course_id=course_id),
-        user=request.user,
         can_execute_unsafe_code=(lambda: can_execute_unsafe_code(course_id)),
         get_python_lib_zip=(lambda: get_python_lib_zip(contentstore, course_id)),
         mixins=settings.XBLOCK_MIXINS,
         course_id=course_id,
-        anonymous_student_id='student',
 
         # Set up functions to modify the fragment produced by student_view
         wrappers=wrappers,
@@ -216,7 +214,7 @@ def _preview_module_system(request, descriptor, field_data):
             "field-data": field_data,
             "i18n": ModuleI18nService,
             "settings": SettingsService(),
-            "user": DjangoXBlockUserService(request.user),
+            "user": DjangoXBlockUserService(request.user, anonymous_user_id='student'),
             "partitions": StudioPartitionService(course_id=course_id),
             "teams_configuration": TeamsConfigurationService(),
         },