This is a reland of 101fd4dd

Original change's description:
> [testrunner] catch unforeseen exceptions
>
> Testrunner doesn't catch exceptions except TestRunnererror, KeyboardInterrupt.
>
> Unforeseen exceptions should fail the CI step.
>
> This CL returns an error exit code for uncaught exceptions.
>
> R=machenbach@chromium.org
> CC=yangguo@chromium.org,sergiyb@chromium.org
>
> Bug: v8:8731
> Change-Id: I7fb20dad4a3eea29f1dfa87ef91d45381ee08692
> Reviewed-on: https://chromium-review.googlesource.com/c/1434034
> Commit-Queue: Tamer Tas <tmrts@chromium.org>
> Reviewed-by: Michael Achenbach <machenbach@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59278}

Bug: v8:8731
No-Try: true
No-Tree-Checks: true
Change-Id: Ic580b334697ecebec923e76ff4a3e09fdf24dc8c
Reviewed-on: https://chromium-review.googlesource.com/c/1449632Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59283}