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

package.json

@@ -115,7 +115,6 @@
     "redux-immutable": "^4.0.0",
     "redux-thunk": "^2.4.1",
     "regenerator-runtime": "^0.13.9",
-    "rellax": "^1.12.1",
     "requestidlecallback": "^0.3.0",
     "reselect": "^4.1.6",
     "rimraf": "^3.0.2",