Create ClusterGroup for each clusterclass with cluster

[richardcase]

What would you like to be added (User Story)?

As an operator
I want a cluster group for all cluster created from the same cluster class
So that i can deploy applications to the clusters

Detailed Description

It would be good to have a Fleet cluster group created for each ClusterClass where a cluster has been created. We should be able to disable this feature if required (globally or at the clusterclass level).

Anything else you would like to add?

This has been added to the addon provider for fleet: rancher-sandbox/cluster-api-addon-provider-fleet#11

Label(s) to be applied

/kind feature

[Danil-Grigorev]

This functionality is a part of CAAPF code, and the feature is marked as experimental. Can be used with integration added with #559