build_api_test.proto: Add a multi-field test message.

Need a generic multi-field test message for the new require_each validator.

BUG=chromium:1130818
TEST=./generate.sh

Change-Id: I5811b08a83a4b7e8d06f4a4acfdf487f1ddb8b60
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2426691
Auto-Submit: Alex Klein <saklein@chromium.org>
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
2 files changed