feat!: change /api/v1/mfe_config to /api/mfe_config/v1

* This changes the API's path. The reasoning is that this is Version 1 of
  the mfe_config API, not Version 1 of the LMS's entire API, so the v1
  should come after mfe_config.
* Why does this matter? Firstly, consistency. Secondly, it affects our
  generated API documentation. If you visited
  https://courses.edx.org/api-docs, you could see that the API was
  listed under "v1" instead of "mfe_config".

lms/djangoapps/mfe_config_api/docs/decisions/0001-mfe-config-api.rst

@@ -18,7 +18,7 @@ Decision
 - A lightweight API will be created that returns the mfe configuration variables from the site configuration or django settings. `PR Discussion about django settings`_
 - The API will be enabled or disabled using the setting ``ENABLE_MFE_CONFIG_API``.
 - The API will take the mfe configuration in the ``MFE_CONFIG`` keyset in the site configuration (admin > site configuration > your domain) or in django settings.
-- This API allows to consult the configurations by specific MFE. Making a request like ``/api/v1/mfe_config?mfe=mymfe`` will return the configuration defined in ``MFE_CONFIG_OVERRIDES["mymfe"]`` merged with the ``MFE_CONFIG`` configuration.
+- This API allows to consult the configurations by specific MFE. Making a request like ``/api/mfe_config/v1?mfe=mymfe`` will return the configuration defined in ``MFE_CONFIG_OVERRIDES["mymfe"]`` merged with the ``MFE_CONFIG`` configuration.
 - The API will have a mechanism to cache the response with ``MFE_CONFIG_API_CACHE_TIMEOUT`` variable.
 - The API will live in lms/djangoapps because this is not something Studio needs to serve and it is a lightweight API. `PR Discussion`_
 - The API will not require authentication or authorization.
@@ -26,7 +26,7 @@ Decision
 
 Request::
 
-    GET http://lms.base.com/api/v1/mfe_config?mfe=learning
+    GET http://lms.base.com/api/mfe_config/v1?mfe=learning
 
 Response::
 

lms/djangoapps/mfe_config_api/views.py

@@ -35,10 +35,10 @@ class MFEConfigView(APIView):
         **Usage**
 
           Get common config:
-          GET /api/v1/mfe_config
+          GET /api/mfe_config/v1
 
           Get app config (common + app-specific overrides):
-          GET /api/v1/mfe_config?mfe=name_of_mfe
+          GET /api/mfe_config/v1?mfe=name_of_mfe
 
         **GET Response Values**
         ```

lms/urls.py

@@ -1028,5 +1028,5 @@ urlpatterns += [
 
 # MFE API urls
 urlpatterns += [
-    path('api/v1/mfe_config', include(('lms.djangoapps.mfe_config_api.urls', 'lms.djangoapps.mfe_config_api'), namespace='mfe_config_api'))
+    path('api/mfe_config/v1', include(('lms.djangoapps.mfe_config_api.urls', 'lms.djangoapps.mfe_config_api'), namespace='mfe_config_api'))
 ]