Description of problem:

In CNV fleet view, we are currently showing all clusters, even if they are not available or if the cluster-proxy addon is not enabled. This leads to errors when trying to use these clusters.

Also! The API useFleetClusterNames has no ts docs, we should add some!

Version-Release number of selected component (if applicable):

ACM 2.15

How reproducible:

Easily

Steps to Reproduce:

1. Using cluster import wizard create a managedCluster but do not complete the import.
2. See CNV fleet view
3. ...

Actual results:

1. unavailable cluster is visible, but when clicked console errs.

   Expected results:

   Additional info: