[ArnobKumarSaha]

Restructures ArgoCDOptions in apis/config/v1alpha1 (selfManagement.argoCD) and apis/cluster:

type ArgoCDOptions struct {
	Enabled       bool
	ManagedArgo   *ManagedArgo   // existingKubeconfig, argoCDClusterName, namespace
	InClusterArgo *InClusterArgo // deployPrincipal, principalServiceType
}

• apis/cluster.ArgoCDOptions keeps principalClusterName at the top level.
• ExistingClusterName is removed. Managed mode now means managedArgo.existingKubeconfig is set.
• argoCDClusterName is the name this cluster is registered under inside the existing Argo CD. It becomes fargocd's clusterName/destName.
• Breaking change: the old flat fields are not accepted.

Note: zz_generated.deepcopy.go was written by hand; please re-run make gen.