🐛 set owner meta on addon resources to prevent deleting out-of-band addons

[arturshadnik]

Description

This PR:

• adds a "addon.open-cluster-management.io/managedBy": fleetconfig-controller label to any ClusterManagementAddOn, AddOnTemplate and ManagedClusterAddOn that is created by FCC
• uses this label to filter the resources when deciding what to delete/disable

This will prevent accidentally deleting addons that are created either manually (helm charts, etc), or using clusteradm.

Sanity testing

• Created 2 kind clusters.
• Installed FCC, created a FleetConfig to register 1 spoke
• Followed https://github.com/open-cluster-management-io/ocm/tree/main/solutions/argocd-agent to install ArgoCD agent addon.
• Verified that prior to these changes, the addon was deleted on the next FC reconcile
• Verified that after the changes, the addon is not deleted by FCC and can be used as expected.

Note: argocd agent addon does not seem to be designed to work with a hub-as-spoke cluster, so it's best to not register the hub as a spoke, or modify the placement to not target the hub-as-spoke

[openshift-ci]

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[ahmad-ibra]

/lgtm