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/features/ui/util/react_router_helpers.js

@@ -53,7 +53,9 @@ export class WrappedRoute extends React.Component {
   }
 
   renderLoading = () => {
-    return <ColumnLoading />;
+    const { multiColumn } = this.props;
+
+    return <ColumnLoading multiColumn={multiColumn} />;
   }
 
   renderError = (props) => {