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/account_timeline/index.js

@@ -142,7 +142,13 @@ class AccountTimeline extends ImmutablePureComponent {
   render () {
     const { accountId, statusIds, featuredStatusIds, isLoading, hasMore, blockedBy, suspended, isAccount, hidden, multiColumn, remote, remoteUrl } = this.props;
 
-    if (!isAccount) {
+    if (isLoading && statusIds.isEmpty()) {
+      return (
+        <Column>
+          <LoadingIndicator />
+        </Column>
+      );
+    } else if (!isLoading && !isAccount) {
       return (
         <Column>
           <ColumnBackButton multiColumn={multiColumn} />
@@ -151,14 +157,6 @@ class AccountTimeline extends ImmutablePureComponent {
       );
     }
 
-    if (!statusIds && isLoading) {
-      return (
-        <Column>
-          <LoadingIndicator />
-        </Column>
-      );
-    }
-
     let emptyMessage;
 
     const forceEmptyState = suspended || blockedBy || hidden;