Ray Cluster Retrieval Function

[Maxusmusti]

Add a function to retrieve ray cluster objects from K8s/OCP, so that people can pick up and resume managing the cluster in fire-and-forget or pipeline scenarios.

[Maxusmusti]

Some implementation details:

In the cluster/cluster.py file, we need a new function:

cluster_retrieval(cluster_name: str, namespace: str = "default") -> Cluster:
    This function should search the k8s/OCP cluster using the specified namespace for a RayCluster with the passed-in 
    name. If found, populate and return a Cluster object with all expected fields (via a ClusterConfig). If not, either return
    None or raise some form of "not found" error or exception.

Note that cluster_retrieval is a place holder name, and if anything better is come up with, it can be used instead.

[MichaelClifford]

@Maxusmusti is there any issue with using the name get_cluster(cluster_name) instead?

[Maxusmusti]

@MichaelClifford Nope, already a better suggestion 😅

[carsonmh]

#189