toolchain_utils: Make DUT config in nightly crosperf default

Remove experiment arguments reducing performance noise from the
buildbot_test_toolchains script and make the values default in
experiment settings.
Add descriptions about default values.

BUG=None
TEST=Tested on local DUT.

Change-Id: I5fa3d5bf36a2ca37da713b42b49c1f2ad4f08c98
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2197549
Tested-by: Denis Nikitin <denik@chromium.org>
Reviewed-by: Zhizhou Yang <zhizhouy@google.com>
3 files changed