cros-publish: throttle GCS upload goroutines to avoid overwhelming bots

Adopt the same logic from the one used by phosphorus.
https://source.chromium.org/chromium/infra/infra/+/main:go/src/infra/libs/skylab/gs/gs.go;l=110;drc=392685e2b84066fa6c958f6e9971d5e69e04c889
- luci.common.sync.parallel.WorkPool is in the existing `dev-go/luci-go-common` dependency that we use for luci.common.errors
- maxConcurrentUploads=10 is same as phosphorus

BUG=b:276770874
TEST=unit test

Change-Id: I69e3819813a2f88cfb51fb155ecaced56230ee27
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/4405057
Reviewed-by: Derek Beckett <dbeckett@chromium.org>
Auto-Submit: Ming Kong <mingkong@google.com>
Tested-by: Ming Kong <mingkong@google.com>
Commit-Queue: Ming Kong <mingkong@google.com>
Reviewed-by: Seewai Fu <seewaifu@google.com>
1 file changed