[test] Be even more verbose when killing hanging tests fails

Basically we expose and put to shame the offending process

R=tmrts@chromium.org

Bug: v8:9855
Change-Id: I322e3f9db487b53e8cbfc8a5edd696fa8b480f84
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1878707
Commit-Queue: Liviu Rau <liviurau@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64555}

tools/testrunner/local/command.py

@@ -134,6 +134,8 @@ class BaseCommand(object):
       self._kill_process(process)
     except OSError as e:
       print(e)
+      started_as = self._to_args_list().to_string(relative=True)
+      print("Unruly process started as:\n  %s\n" % started_as)
       sys.stdout.flush()
       pass