toolchain-utils: migrate all in-use projects to python 3

This patch migrates all in-use projects left to python 3.

BUG=chromium:1011676
TEST=Passed unittests and launched scripts manually.

Change-Id: I7f2de4e1131c05bacfac80667f3064da8adaebfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2051397
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Zhizhou Yang <zhizhouy@google.com>
Auto-Submit: Zhizhou Yang <zhizhouy@google.com>
29 files changed