Remove duplicate compact settings, handle device level updates

This removes the duplicate setting for compact layout from the appearance tab,
and leaves the "advanced" one, matching the intention from Design.

This also adds the relevant handling to ensure the device-level setting triggers
an update immediately when changed.

Fixes https://github.com/vector-im/riot-web/issues/14304

src/components/structures/LoggedInView.tsx

@@ -146,6 +146,7 @@ class LoggedInView extends React.Component<IProps, IState> {
     protected readonly _resizeContainer: React.RefObject<ResizeHandle>;
     protected readonly _sessionStore: sessionStore;
     protected readonly _sessionStoreToken: { remove: () => void };
+    protected readonly _compactLayoutWatcherRef: string;
     protected resizer: Resizer;
 
     constructor(props, context) {
@@ -177,6 +178,10 @@ class LoggedInView extends React.Component<IProps, IState> {
         this._matrixClient.on("sync", this.onSync);
         this._matrixClient.on("RoomState.events", this.onRoomStateEvents);
 
+        this._compactLayoutWatcherRef = SettingsStore.watchSetting(
+            "useCompactLayout", null, this.onCompactLayoutChanged,
+        );
+
         fixupColorFonts();
 
         this._roomView = React.createRef();
@@ -194,6 +199,7 @@ class LoggedInView extends React.Component<IProps, IState> {
         this._matrixClient.removeListener("accountData", this.onAccountData);
         this._matrixClient.removeListener("sync", this.onSync);
         this._matrixClient.removeListener("RoomState.events", this.onRoomStateEvents);
+        SettingsStore.unwatchSetting(this._compactLayoutWatcherRef);
         if (this._sessionStoreToken) {
             this._sessionStoreToken.remove();
         }
@@ -263,16 +269,17 @@ class LoggedInView extends React.Component<IProps, IState> {
     }
 
     onAccountData = (event) => {
-        if (event.getType() === "im.vector.web.settings") {
-            this.setState({
-                useCompactLayout: event.getContent().useCompactLayout,
-            });
-        }
         if (event.getType() === "m.ignored_user_list") {
             dis.dispatch({action: "ignore_state_changed"});
         }
     };
 
+    onCompactLayoutChanged = (setting, roomId, level, valueAtLevel, newValue) => {
+        this.setState({
+            useCompactLayout: valueAtLevel,
+        });
+    };
+
     onSync = (syncState, oldSyncState, data) => {
         const oldErrCode = (
             this.state.syncErrorData &&