Has different protobuf guts. The only observable side effect is different
formatting of generated files. But 'lucicfg validate' now compares files
semantically, so different formatting shouldn't matter.

There's a bunch of other internal changes, but clients that rely on them are
already aware and updated.

R=iannucci@chromium.org
BUG=986972

Change-Id: Ifd13c453736e438f28c2cf938003dce00f2cb199
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1769607Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>