Disable unsupported clusters in cluster dropdown

As a developer I would like to disable clusters like *KS that we can't support for multi-cluster (for instance because we can't authenticate). The ManagedCluster resource has a vendor label that we can use to know if the cluster is supported.

cc amobrem showeimer jhadvig@redhat.com 

UPDATE: 9/20/22 : we want an allow-list with OpenShift, ROSA, ARO, ROKS, and  OpenShiftDedicated

Acceptance criteria:

• Investigate if console-operator should pass info about which cluster are supported and unsupported to the frontend
• Unsupported clusters should not appear in the cluster dropdown
• Unsupported clusters based off
  • defined vendor label
  • non 4.x ocp clusters