Create a way to stage an entire relation chain or topic in Gerrit

When a series of changes get staged together and then the CI fails the integration due to an unrelated issue, the entire chain must be manually restaged, change by change.

This can be time consuming if there are many changes, and doubly so when an integration fails multiple times.

Ideally, this would be implemented in Gerrit itself.

Suggestions:

• If a change is part of a relation change, clicking Stage could pop a window with the option to stage the entire chain. The dialog should show the list of changes to stage with an indicator of staging-readiness.
• Add a second stage button when the change is part of a relation chain to stage all. Pop a dialog if not all changes are eligible to stage.