Benchy: integrate with benchmark mode games tuning workload

Extend benchy to handle benchmark mode games tuning workload, mainly the
parsing of the metrics.

BUG=b:247167973
TEST=./benchy create --sample | ./benchy run results with workload as
borealis.Benchmark.metroll_redux

Change-Id: Ic24ae6c9baa347386a2094926afb1d90abf2651d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/graphics/+/4015803
Tested-by: Suhua Lei <lsuhua@google.com>
Reviewed-by: David Riley <davidriley@chromium.org>
Commit-Queue: Suhua Lei <lsuhua@google.com>