[flaky test reporting] print stack trace for flaky reruns (#77664)
Give context about failures ~and include it in the test report~! Unfortunately I cannot include it easily in the test report through the addExpectedFailures :c as tracebacks are not something I can instantiate. (see revert comment)
Current way doesn't print the stack traces, which has been fine because we don't hide the signal and it shows up at the end:
<img width="545" alt="image" src="https://user-images.githubusercontent.com/31798555/168878182-914edc39-369f-40bc-8b35-9d5cd47a6b1c.png">
However, when we want to hide the signal, we'd like to print the stack traces for each failed attempt, as it won't be shown at the end.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77664
Approved by: https://github.com/suo
