feat: add virtualization cluster type, group, and cluster sync support

[abhimanyu003]

This PR introduces full CRUD sync support to three new resource types

• Cluster Types
• Cluster Groups
• Clusters

Sample YAML

Cluster types:

- name: "vmware"
  description: "VMware vSphere cluster"

Cluster groups:

- name: "us-east-production"
  description: "Production clusters in US East"

Clusters:

- name: "prod-cluster-01"
  comments: "Primary production cluster"
  cluster_type: "vmware"
  cluster_group: "us-east-production"
  location: "US-East-DC1"
  devices:
    - "server-01"
    - "server-02"

CR spec additions

The Nautobot custom resource now accepts three new optional refs:

spec:
  clusterTypeRef:
    - configMapSelector:
        name: cluster-types-config
        namespace: default
  clusterGroupRef:
    - configMapSelector:
        name: cluster-groups-config
        namespace: default
  clusterRef:
    - configMapSelector:
        name: clusters-config
        namespace: default

[abhimanyu003]

Removing this Name fields as it's dead weight. It adds a required field to the CRD that users have to fill in but the operator never reads.
It creates confusion too, since both ConfigMapRef.Name and ConfigMapRef.ConfigMapSelector.Name exist as "name" at different nesting levels in the YAML.