apply_event: Do not include new user settings in the top level.

From 430c5cb, in `fetch_initial_state_data`,
we only include legacy settings in the top level of
`state` and the newer ones are stored in `state['user_settings']`.
That should've had a corresponding change in apply_event().

Also, fixed a test related to this logic.

zerver/lib/events.py

@@ -1197,7 +1197,11 @@ def apply_event(
         # this setting is not a part of UserBaseSettings class.
         if event["property"] != "timezone":
             assert event["property"] in UserProfile.property_types
-        state[event["property"]] = event["value"]
+        if event["property"] in {
+            **UserProfile.display_settings_legacy,
+            **UserProfile.notification_settings_legacy,
+        }:
+            state[event["property"]] = event["value"]
         state["user_settings"][event["property"]] = event["value"]
     elif event["type"] == "invites_changed":
         pass

zerver/tests/test_event_system.py

@@ -564,7 +564,12 @@ class FetchInitialStateDataTest(ZulipTestCase):
         )
         self.assertIn("user_settings", result)
         for prop in UserProfile.property_types:
-            self.assertIn(prop, result)
+            if prop in {
+                **UserProfile.display_settings_legacy,
+                **UserProfile.notification_settings_legacy,
+            }:
+                # Only legacy settings are included in the top level.
+                self.assertIn(prop, result)
             self.assertIn(prop, result["user_settings"])