This change also adds a ScoreOwners function in owners_client
that replaces user scoring functionality in owners_finder.

Change-Id: Ifd8841c6d320d9bb644907b6eca0a02d4ef35640
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2641532Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Gavin Mak <gavinmak@google.com>