feat: [Hackathon12-D2864]: Use CCO CRD NutanixPrismCentral to replac…

[yanhua121]

Use CCO CRD NutanixPrismCentral to replace pcEndpoint in NutanixCLuster spec, using the reference in NutanixFailureDomain spec.

The NutanixPrismCentral CRD is introduced at https://github.com/nutanix-engineering/hack2026-d2864/.

1. NutanixPrismCentral CRD
   This CRD can be used to decouple PC endpoint info from the NutanixCluster spec, making failure domains and PC endpoints/credentials first-class, reusable entities.

• Purpose: To support Cross-Prism Central (Multi-PC) topologies and decouple failure domain definitions from the cluster spec.
• Structure:Scope: Namespaced.
• Spec: Contains the NutanixPrismEndpoint definition (Address, Port, Insecure flag) and a CredentialRef.
• CredentialRef: A reference to a generic Kubernetes Secret containing the actual username/password.
  Usage:Referenced by the NutanixFailureDomain CRD.
  Allows a single CAPX cluster to span multiple availability zones (Prism Elements) potentially managed by different Prism Centrals.
• Replaces the embedded failureDomains list in NutanixCluster and makes the global spec.prismCentral field optional (used only as a fallback).