Add tool to reformat testing/buildbot/ json files in their canonical format.

The tool is now run as presubmit check.

It enforces key sorting and upgrades gtest_tests to the dict format.

No functional change.

R=phajdan.jr@chromium.org
BUG=98637

Review URL: https://codereview.chromium.org/1049703005

Cr-Commit-Position: refs/heads/master@{#323217}
19 files changed