Implement agent initiated selection logic for Clusters using ClusterClass based on jsonPatch name

[Danil-Grigorev]

In order to distinguish clusters using agent-initiated registration method, CAAPF would need to match against:

• Cluster or namespace label selectors, defined in the FleetAddonConfig resource.
• Clusters using a ClusterClass by referencing some in topology.class.
• ClusterClass referenced by the Cluster containing a fleet-agent-install jsonPatch.

By ensuring that cluster class has this patch, we restrict agent initiated installation path only to clusters following this contract. It will be up to the cluster class owner to define patch properly, for which we need to add documentation page with instructions and examples (covered by #247)