Swarming server Go code

To deploy from a local checkout:

gae.py upload -A chromium-swarm-dev default-go

To run locally using fake bots and tasks (but with real Datastore and real RBE):

# Terminal 1: launch the server locally and keep it running.
cd server/cmd
go run main.go \
  -cloud-project chromium-swarm-dev \
  -shared-hmac-secret devsecret://aaaa \
  -expose-integration-mocks

# Terminal 2: launch a fake bot and keep it running.
cd server/testing/fakebot
go run main.go -bot-id fake-bot-1 -pool "${USER}-local-test"

# Terminal 3: launch a task and see it handled by the fake bot.
cd server/testing/fakesubmit
go run main.go -pool "${USER}-local-test"

Note that these tests hit real RBE instance (by default default_instance in chromium-swarm-dev project), so they may theoretically interfere with other similar tests running on other machines or even with real chromium-swarm-dev RBE traffic. pool dimension can be used to namespace them.