Resolve "Show canary / no-canary in the performance bar"

What does this MR do?

In the performance bar, show a bird emoji, and colour the hostname in yellow, if you're on a canary host.

In production, it will look like this:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug

Closes #52421 (closed).

app/assets/javascripts/performance_bar/components/performance_bar_app.vue

 <script>
 import $ from 'jquery';
+import { glEmojiTag } from '~/emoji';
 
 import detailedMetric from './detailed_metric.vue';
 import requestSelector from './request_selector.vue';
@@ -64,6 +65,16 @@ export default {
     lineProfileModal() {
       return $('#modal-peek-line-profile');
     },
+    hasHost() {
+      return this.currentRequest && this.currentRequest.details && this.currentRequest.details.host;
+    },
+    birdEmoji() {
+      if (this.hasHost && this.currentRequest.details.host.canary) {
+        return glEmojiTag('bird');
+      }
+
+      return '';
+    },
   },
   mounted() {
     this.currentRequest = this.requestId;
@@ -93,9 +104,11 @@ export default {
         class="view"
       >
         <span
-          v-if="currentRequest.details"
+          v-if="hasHost"
           class="current-host"
+          :class="{ 'canary' : currentRequest.details.host.canary }"
         >
+          <span v-html="birdEmoji"></span>
           {{ currentRequest.details.host.hostname }}
         </span>
       </div>