crosperf: migration to python 3

This patch migrates crosperf and its utils to python 3.

TEST=Passed presubmit check; tested with simple experiment locally.
BUG=chromium:1011676

Change-Id: Ib2a9f9c7cf6a1bb1d0b42a1dd3d9e3cbb4d70a36
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2003796
Tested-by: Zhizhou Yang <zhizhouy@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>
Commit-Queue: Zhizhou Yang <zhizhouy@google.com>
Auto-Submit: Zhizhou Yang <zhizhouy@google.com>
44 files changed