Change public accounts pages to mount the web UI (#19319)

* Change public accounts pages to mount the web UI

* Fix handling of remote usernames in routes

- When logged in, serve web app
- When logged out, redirect to permalink
- Fix `app-body` class not being set sometimes due to name conflict

* Fix missing `multiColumn` prop

* Fix failing test

* Use `discoverable` attribute to control indexing directives

* Fix `<ColumnLoading />` not using `multiColumn`

* Add `noindex` to accounts in REST API

* Change noindex directive to not be rendered by default before a route is mounted

* Add loading indicator for detailed status in web UI

* Fix missing indicator appearing while account is loading in web UI

app/javascript/mastodon/containers/mastodon.js

@@ -78,7 +78,7 @@ export default class Mastodon extends React.PureComponent {
       <IntlProvider locale={locale} messages={messages}>
         <ReduxProvider store={store}>
           <ErrorBoundary>
-            <BrowserRouter basename='/web'>
+            <BrowserRouter>
               <ScrollContext shouldUpdateScroll={this.shouldUpdateScroll}>
                 <Route path='/' component={UI} />
               </ScrollContext>