The ClusterDeployment should be registered independent of InfraEnv. Cluster registration should start only after the ClusterDeployment manifest files (cluster-deployment.yaml and agent-cluster-install.yaml) are available. If any of those files are missing, the missing file should be logged by the client, and the client should retry after a timeout. 

Current flow:

• Client registers ClusterDeployment and InfraEnv sequentially.
• If ClusterDeployment registration fails, InfraEnv is not registered.
• If ClusterDeployment registration is successful, client then registers InfraEnv.

Proposed Change: 

• Split Cluster registration into its own service: agent-register-cluster.service
• Update agent-installer-client to create a new "register-cluster" command.
• agent-register-cluster.service waits for ClusterDeployment and AgentClusterInstall manifest to be present on the file system. If they are not present, the client waits and tries again after a sleep.
• When both manifests are present, the client registers the ClusterDeployment with assisted-service.
• If there are extra manifests present on the filesystem, this service also adds them to the Cluster through the assisted-service REST-API.

Acceptance Criteria:

• agent-register-cluster.service does not fail if ClusterDeployment and/or AgentClusterInstall manifests are not available. The install client continues to poll the file system until the manifests appear.
• Cluster is registered when cluster-deployment.yaml and agent-cluster-install.yaml manifests are made available under /etc/manifests.
• Cluster is updated with extra manifests if they exist at the time the cluster is registered.

This story only for assisted-service repo change to agent-installer-client.