Merge branch 'migrate-js-pipelines-event-hub-to-mitt' into 'master'

Migrate event hub to mitt in js/pipelines

Closes #216820

See merge request gitlab-org/gitlab!37642

app/assets/javascripts/pipelines/event_hub.js

-import Vue from 'vue';
+import createEventHub from '~/helpers/event_hub_factory';
 
-export default new Vue();
+export default createEventHub();