Also, update to the latest tag rather than one from 2019. This is in
preparation for changing the host config to use a specific image tag
instead of baking the image tag into every docker image.

This change will allow us to keep a separate 'cloudbuild' tag from the
tag used for the main bulder. This tag can be updated weekly, allowing
us to run a second builder in parallel to determine when we want to
update to a newer image.

For golang/go#56673

Change-Id: I906a95b447949deba0b108b3009c440aa5c31171
Reviewed-on: https://go-review.googlesource.com/c/build/+/449037
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Jenny Rakoczy <jenny@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

This changes where the container image is build and publishes it to
the container registry. Cloud Build is used to create and publish the
coordinator container image.

Updates golang/go#56673

Change-Id: I6811c59fe06f7507e576baf10b12fc09d1212174
Reviewed-on: https://go-review.googlesource.com/c/build/+/460355
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>

This change specifies the project in the cloud build image command.

For golang/go#56673

Change-Id: Ib275c2b42d4cf0930b1ac56be876ce0683643b6e
Reviewed-on: https://go-review.googlesource.com/c/build/+/479836
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Carlos Amedee <carlos@golang.org>
Auto-Submit: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>