luci-go @ b8f8bf3582b0bed4cde222f538b4ff04c0b0cfc0.

Backwards compatible.

Includes experimental CQ cancelation feature
and a bugfix for CQ groups w/o any builders.

R=vadimsh

note: roll will be trivial, footer below just for autoroller to let this CL in.
Recipe-Nontrivial-Roll: skia
Change-Id: Ief596c260276fc461d3dc473a7b89e20e863b965
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1620806
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Auto-Submit: Andrii Shyshkalov <tandrii@chromium.org>