Automate verification of the documented deployment steps

[barroco]

Following up on #874 , we want to be able to test in the CI/CD the deployment of a DSS Region with multi-cloud DSS instances and test the pooling procedure as documented.

Deployment to AWS is already possible via CI here: https://github.com/interuss/dss/tree/master/deploy/operations/ci/aws-1

Objectives:

1. Enabling the CI to deploy to GCP, some pre-work is required to secure the cloud account in order to issue a secure service account for the CI.
2. Ensure the steps performed corresponds to the ones documented in the user guide.