Add Go proto bindings.

- Create go mod "go.chromium.org/chromiumos/config/go".
Bindings have package name <od name + directory
structure relative to "proto"; for example,
proto/api/build_config.proto has go package
"go.chromium.org/chromiumos/config/go/api".

- Change protoc search root to proto/, to remove the "src/config" from
generating proto binding paths. This requires updating the Python and
Starlark proto import paths.

- Also rename chromeos-config to chromeos_config, for consistency
with other packages.

BUG=chromium:1055346
TEST=./generate.sh
TEST=go build ...
TEST=python unittests

Cq-Depend: chrome-internal:2626583, chrome-internal:2626693
Change-Id: I2f6671c8f045b36621936cc192be8ec62f42aac7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/config/+/2070676
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: David Burger <dburger@chromium.org>
Tested-by: Andrew Lamb <andrewlamb@chromium.org>
Commit-Queue: Andrew Lamb <andrewlamb@chromium.org>
61 files changed