REFACTOR: Remove Discourse.SiteSettings from utilities

This involves a little refactoring of how our `defaultHomepage()` works.
It previously would check the meta tag / site settings each time it was
called but now it only checks once on application boot.

test/javascripts/acceptance/login-redirect-test.js

@@ -1,7 +1,6 @@
 import { acceptance } from "helpers/qunit-helpers";
 
-acceptance("Login redirect", {});
-
+acceptance("Login redirect");
 QUnit.test("redirects login to default homepage", async function(assert) {
   await visit("/login");
   assert.equal(
@@ -9,8 +8,15 @@ QUnit.test("redirects login to default homepage", async function(assert) {
     "discovery.latest",
     "it works when latest is the homepage"
   );
-  this.siteSettings.top_menu = "categories|latest|top|hot";
+});
 
+acceptance("Login redirect - categories default", {
+  settings: {
+    top_menu: "categories|latest|top|hot"
+  }
+});
+
+QUnit.test("when site setting is categories", async function(assert) {
   await visit("/login");
   assert.equal(
     currentPath(),