DEV: Move discourse.js to app/app.js (#9545)

This is another thing to get our application in line with what Ember CLI
expects.

app/assets/javascripts/application.js

@@ -5,7 +5,7 @@
 //= require ./ember-addons/fmt
 //= require ./polyfills
 //= require_tree ./select-kit
-//= require ./discourse
+//= require ./discourse/app/app
 //= require ./deprecated
 
 // Stuff we need to load first

app/assets/javascripts/deprecated.js

@@ -1,4 +1,4 @@
 // ensure Discourse is added as a global
 (function() {
-  window.Discourse = requirejs("discourse").default;
+  window.Discourse = requirejs("discourse/app").default;
 })();

app/assets/javascripts/discourse-loader.js

@@ -263,6 +263,14 @@ var define, requirejs;
   function requireFrom(name, origin) {
     name = transformForAliases(name);
 
+    if (name === "discourse") {
+      // eslint-disable-next-line no-console
+      console.log(
+        "discourse has been moved to `discourse/app` - please update your code"
+      );
+      name = "discourse/app";
+    }
+
     if (name === "discourse/models/input-validation") {
       // eslint-disable-next-line no-console
       console.log(

app/assets/javascripts/discourse/app/pre-initializers/inject-discourse-objects.js

@@ -2,7 +2,7 @@ import Session from "discourse/models/session";
 import KeyValueStore from "discourse/lib/key-value-store";
 import Store from "discourse/models/store";
 import DiscourseLocation from "discourse/lib/discourse-location";
-import Discourse from "discourse";
+import Discourse from "discourse/app";
 import SearchService from "discourse/services/search";
 import TopicTrackingState, {
   startTracking