Enhance the output of PlacementDecision by including more details about the managed cluster

[mikeshng]

The PlacementDecision returns the set of managed cluster clusterNames.

status:
  decisions:
    - clusterName: cluster1
    - clusterName: cluster2
    - clusterName: cluster3

It maybe helpful to return other data as well such as the clusterClaims associated with the managed cluster along with the clusterName. This should be an opt-in only feature depending on the Placement spec.

Use case:

1. The ArgoCD Cluster Decision Resource Generator uses duck-typing to specify the PlacementDecision in order to grab the set of OCM clusterNames for ApplicationSet template evaluation. In addition to clusterNames, it will be nice to have other details about the clusters as well so that more templating variables can be used.

2. Allows human users and API consumers to generate a report on managed clusters easily.

[mikeshng]

CC @haoqing0110 @qiujian16

[github-actions]

Message to comment on stale issues. If none provided, will not mark issues stale

[github-actions]

This issue is stale because it has been open for 120 days with no activity. After 14 days of inactivity, it will be closed. Remove the stable label to prevent this issue from being closed.

[github-actions]

This issue is stale because it has been open for 120 days with no activity. After 14 days of inactivity, it will be closed. Remove the stable label to prevent this issue from being closed.