Print tools/perf/run_benchmark list on stdout instead of stderr
Print tools/perf/run_benchmark list on stdout instead of stderr

This patch changes tools/perf/run_benchmark to output the list command
on stdout instead of stderr. This makes grepping for benchmarks easier.

Note: The run command will still output the benchmark list on stderr if
an invalid benchmark is specified.

Review URL: https://codereview.chromium.org/948793002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#317712}

benschmaus/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult,sahiljain/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,benschmaus/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,sahiljain/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,sahiljain/catapult