Summary:
Extend NodeSpec in the ClusterInstance CRD by introducing the HostRef (with Name and Namespace sub-fields) field to enable referencing node resources (BareMetalHost, InfraEnv, etc) across different namespaces. Additionally, update the Assisted Installer (AI) and Image-Based Installer (IBI) installation templates to align with this change.

Description:
This task involves enhancing the ClusterInstance CRD and its associated installation templates to improve flexibility in multi-namespace deployments. The key updates include:

• Introduce HostRef in NodeSpec to allow referencing BareMetalHost in a namespace different from the cluster.
• Refactor AI installation templates to define InfraEnv at the node level instead of the cluster level, ensuring a new InfraEnv is created per BareMetalHost.
• Update NMStateConfig (for AI) and NetworkSecret (for IBI) to be created in the same namespace as BareMetalHost when HostRef is specified.
• Improve test coverage by adding test suites to verify:
  • Expected installation templates for AI and IBI.
  • Successful parsing of the templates.