These tools are used by scripts/trigger.py and by the src-side testing.
Also adds .vpython and .vpython3 spec files which can't be easily
auto-rolled from the Chromium src/ repo.

Bug: angleproject:5040
Change-Id: Ie6384c176b391dae4fe19582ec59c2c1d6ec22d8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2408717
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>