Support workspaces e2e test to work with an existing cluster setup

Support the existing e2e test to be run against a long-lived sandbox environment where the following pre-requisties would already be setup:

1. GKE cluster available
2. Ingress will be installed
3. A domain for the workspaces pointing to the load balancer would be available
4. Gitlab-workspaces proxy would be setup with the existing domain

During the e2e test, the test would do the following

1. Create a agent project, and connect the agent to the existing GKE cluster
2. Add agent config file with dns zone pointing to the above domain
3. Create a devfile for a public project ( with a app)
4. Create a new workspace for the above devfile project
5. Continue with the other tests with the new workspace created