Gerrit API doesn't provide the score for
an owner of a path, so we can't use the
same algorithm when suggesting owners.

This change introduces a new algorithm to
select the smallest set of at least 2
owners that can approve the change.

Change-Id: If620073bdf63633f171c1480e345dbaf75e9f575
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2556479Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>