DEV: Add loading spinner to history modal (#22666)

https://github.com/discourse/discourse/assets/50783505/b5f510a8-719c-461c-a02f-a8b3a8573466

app/assets/javascripts/discourse/app/components/modal/history.hbs

@@ -4,6 +4,7 @@
   class="history-modal"
 >
   <:body>
+    <ConditionalLoadingSpinner @condition={{this.loading}}>
       <Modal::History::Revision
         @model={{this.postRevision}}
         @mobileView={{this.site.mobileView}}
@@ -31,6 +32,7 @@
         @calculateBodyDiff={{this.calculateBodyDiff}}
         @titleDiff={{this.titleDiff}}
       />
+    </ConditionalLoadingSpinner>
   </:body>
   <:footer>
     {{#if @model.editPost}}

app/assets/javascripts/discourse/app/components/modal/history.js

@@ -168,8 +168,8 @@ export default class History extends Component {
   refresh(postId, postVersion) {
     this.loading = true;
     Post.loadRevision(postId, postVersion).then((result) => {
-      this.loading = false;
       this.postRevision = result;
+      this.loading = false;
     });
   }
 

app/assets/javascripts/discourse/app/components/modal/history/revisions.hbs

@@ -68,6 +68,7 @@
 
   <LinksRedirect
     @class="row body-diff"
+    {{did-insert @calculateBodyDiff @bodyDiffHTML}}
     {{did-update @calculateBodyDiff @bodyDiffHTML}}
   >
     {{html-safe @bodyDiff}}

app/assets/javascripts/discourse/tests/acceptance/edit-notification-click-test.js

@@ -42,7 +42,6 @@ acceptance("Edit Notification Click", function (needs) {
     await visit("/");
     await click(".header-dropdown-toggle.current-user");
     await click(".notification.edited a");
-
     const [v1, v2] = queryAll(".history-modal .revision-content");
 
     assert.strictEqual(