Stress: show "node upgraded/migrated" status if your pod was killed

Currently we have to enforce an upgrade window for our nodes, which means that some long-running pods can be killed earlier than expected.

To make it simpler for people to track we should show a note or status in the dashboard telling you that that's the reason your pod failed so you don't assume it's something incorrect about your stress test.

(We should also look at the UX of this too to see how bad/good this looks without any work on our part)