refactor: deprecates ModuleSystem.render_template

in favor of the added MakoSystem render_template method.

Related changes:
* Adds the MakoService to the StudioEditModuleRuntime,
  PreviewModuleSystem, LmsModuleSystem, and XBlockRuntime
* MakoService constructor takes a `namespace_prefix` string, so that the
  CMS PreviewModuleSystem can render to LMS templates, without needing
  the special render_from_lms helper method.
* ModuleSystem.render_template becomes a read-only property, so the
  constructor calls and test module systems are updated accordingly.
* Adds tests for the MakoService and module system shims.

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

@@ -19,6 +19,7 @@ from xblock.field_data import SplitFieldData
 from xblock.fields import Scope
 from xblock.runtime import KvsFieldData, MemoryIdManager, Runtime
 
+from common.djangoapps.edxmako.services import MakoService
 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
@@ -235,6 +236,8 @@ class XBlockRuntime(RuntimeShim, Runtime):
                 user_is_staff=self.user.is_staff,
                 anonymous_user_id=self.anonymous_student_id,
             )
+        elif service_name == "mako":
+            return MakoService()
         elif service_name == "i18n":
             return ModuleI18nService(block=block)
         # Check if the XBlockRuntimeSystem wants to handle this: