refactor: migrate account-menu to react - implement functionality

- remove all Angular code related to `account-menu`
- rename React component to AccountMenu so that many parts of old code remain unchanged
- code cleanup

app/assets/javascripts/components/ConfirmSignoutModal.tsx

@@ -15,13 +15,10 @@ type Props = {
   appState: AppState;
 };
 
-const ConfirmSignoutContainer = observer((props: Props) => {
+export const ConfirmSignoutContainer = observer((props: Props) => {
   if (!props.appState.accountMenu.signingOut) {
     return null;
   }
-  if (!props.appState.accountMenuReact.signingOut) {
-    return null;
-  }
   return <ConfirmSignoutModal {...props} />;
 });
 
@@ -33,14 +30,13 @@ const ConfirmSignoutModal = observer(({ application, appState }: Props) => {
   const cancelRef = useRef<HTMLButtonElement>();
   function close() {
     appState.accountMenu.setSigningOut(false);
-    appState.accountMenuReact.setSigningOut(false);
   }
 
   const [localBackupsCount, setLocalBackupsCount] = useState(0);
 
   useEffect(() => {
     application.bridge.localBackupsCount().then(setLocalBackupsCount);
-  }, [appState.accountMenu.signingOut, appState.accountMenuReact.signingOut, application.bridge]);
+  }, [appState.accountMenu.signingOut, application.bridge]);
 
   return (
     <AlertDialog onDismiss={close} leastDestructiveRef={cancelRef}>