proto: add request_tag to ExecutionTask for tracking its request in CTP

BUG=chromium:1113378
TEST=generate.sh

Change-Id: I53ea03ecaaba9148071061e29b1617e255ddca18
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2340167
Commit-Queue: Xinan Lin <linxinan@chromium.org>
Tested-by: Xinan Lin <linxinan@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
2 files changed