[2XL Linux] 3. Configure GCP projects in terraform

Configure the new xxl projects through terraform. Add all remaining configuration in terraform for xxl runners.

reference MR on previous configuration for xl runners: https://ops.gitlab.net/gitlab-com/gl-infra/config-mgmt/-/merge_requests/6029

Note: Everything under .gitlab/ci is auto-generated after:

1. Add environment name in .gitlab/ci/main.jsonnet
2. Run make generate-ci-config

The new environment folder you'll add, similar to r-saas-l-m-‎amd64-org, is a copy of that, with an update to remote_backend.tf and variables.tf.