FIX: Latest post created_at on topic-timeline not updating (#20665)

# Context
https://meta.discourse.org/t/timeline-timestamp-not-updating/256447/1

During the upgrade of the topic-timeline to glimmer the "latest post" timestamp was not updating on the timeline in relation to the relative age of the post. It was only updating on a hard refresh.

# Fix
Use the `age-with-tooltip` helper to update the created_at date automatically as time passes.

# Additional
Add the ability to pass params to `age-with-tooltip` so that we can include options like `addAgo` and `defaultFormat`

app/assets/javascripts/discourse/app/components/topic-timeline/container.hbs

@@ -105,13 +105,9 @@
     </div>
 
     <div class="timeline-date-wrapper">
-      <a
-        class="now-date"
-        onClick={{this.updatePercentage}}
-        title={{this.nowDate}}
-      >
+      <a class="now-date" onClick={{this.updatePercentage}}>
         <span>
-          {{this.nowDate}}
+          {{age-with-tooltip this.nowDate this.nowDateOptions}}
         </span>
       </a>
     </div>

app/assets/javascripts/discourse/app/components/topic-timeline/container.js

@@ -1,7 +1,6 @@
 import Component from "@glimmer/component";
 import { tracked } from "@glimmer/tracking";
 import { action } from "@ember/object";
-import { relativeAge } from "discourse/lib/formatter";
 import I18n from "I18n";
 import { htmlSafe } from "@ember/template";
 import { inject as service } from "@ember/service";
@@ -153,22 +152,21 @@ export default class TopicTimelineScrollArea extends Component {
     return this.lastReadTop > bottom ? bottom : this.lastReadTop;
   }
 
-  get bottomAge() {
-    return relativeAge(
-      new Date(this.args.model.last_posted_at || this.args.model.created_at),
-      {
-        addAgo: true,
-        defaultFormat: timelineDate,
-      }
-    );
-  }
-
   get startDate() {
     return timelineDate(this.args.model.createdAt);
   }
 
+  get nowDateOptions() {
+    return {
+      addAgo: true,
+      defaultFormat: timelineDate,
+    };
+  }
+
   get nowDate() {
-    return this.bottomAge;
+    return (
+      this.args.model.get("last_posted_at") || this.args.model.get("created_at")
+    );
   }
 
   get lastReadHeight() {

app/assets/javascripts/discourse/app/helpers/application.js

@@ -10,8 +10,14 @@ import { registerUnbound } from "discourse-common/lib/helpers";
 
 registerUnbound("raw-date", (dt) => htmlSafe(longDate(new Date(dt))));
 
-registerUnbound("age-with-tooltip", (dt) =>
-  htmlSafe(autoUpdatingRelativeAge(new Date(dt), { title: true }))
+registerUnbound("age-with-tooltip", (dt, params) =>
+  htmlSafe(
+    autoUpdatingRelativeAge(new Date(dt), {
+      title: true,
+      addAgo: params.addAgo || false,
+      ...(params.defaultFormat && { defaultFormat: params.defaultFormat }),
+    })
+  )
 );
 
 registerUnbound("number", (orig, params) => {