Pipeline stages dropdown is out of sync

Problem

After rolling out and working on #223264 I noticed that with a subscription the overall stage status is accurate but the job status within the stage is not. Which makes sense because we get real-time updates via a webscocket for the stages.

However app/assets/javascripts/ci/pipeline_mini_graph/pipeline_stage_dropdown.vue using polling which makes it not in sync. I mean it never really was to begin with, but let's fix that.

Potential solutions

1. We could refactor any upstream subscriptions to feed not just the stages but the jobs as well. Don't love this idea because that's a lot of nested data to fetch.
2. We could refactor app/assets/javascripts/ci/pipeline_mini_graph/pipeline_stage_dropdown.vue to fetch fresh jobs each time it's open if the state of those jobs statuses have changed (still might be a little out of sync 🤷)
3. We could build a dedicated stage subscription and use directly in app/assets/javascripts/ci/pipeline_mini_graph/pipeline_stage_dropdown.vue