System groups (#18303)

* Add read only and admin policies

* Migrate to 2 system groups

* Add system groups

* Add system groups admin & read only

* Dont' mutate parameters

* Fix types

tests/common.py

@@ -15,6 +15,7 @@ from contextlib import contextmanager
 from homeassistant import auth, core as ha, config_entries
 from homeassistant.auth import (
     models as auth_models, auth_store, providers as auth_providers)
+from homeassistant.auth.permissions import system_policies
 from homeassistant.setup import setup_component, async_setup_component
 from homeassistant.config import async_process_component_config
 from homeassistant.helpers import (
@@ -349,7 +350,7 @@ class MockGroup(auth_models.Group):
     """Mock a group in Home Assistant."""
 
     def __init__(self, id=None, name='Mock Group',
-                 policy=auth_store.DEFAULT_POLICY):
+                 policy=system_policies.ADMIN_POLICY):
         """Mock a group."""
         kwargs = {
             'name': name,