[Metrics] Fix help text for run_metric + add failure pretty printing
[Metrics] Fix help text for run_metric + add failure pretty printing

BUG=catapult:#2200
R=nduca

Review URL: https://codereview.chromium.org/1849183005

catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult-csm,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult-csm,sahiljain/catapult,sahiljain/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,benschmaus/catapult,sahiljain/catapult,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult-csm,benschmaus/catapult