Draft: Update preferred pipeline events

This MR will update the pipeline preferred events in the case where a preferred pipeline event needs to be updated but the preferred event does not. Currently gracedb automatically updates the pipeline preferred events when the preferred event is updated, but otherwise it doesn't adjust the field.

This is marked as a draft for now because the following items still need to be completed:

• Add button to views to update preferred pipeline event
• Add new unit test (if needed?)
• Test on emfollow-test