Follow-up from "Integrate new pipeline query for pipeline editor"

Let's update the polling in the Pipeline Editor to use Etag caching instead of sending the query each time.

This will take two steps:

• Updating the backend so that this query/route is cached.
• Making it possible for the Etag resource path to update with the commit — probably by passing it in the query, but alternately by creating a frontend path utility.

This is a followup to !54888 (merged)