Improve GB200 networking, runtime idempotency, Docker pinning, and Ubuntu keyring handling

[ericrife]

Summary

This PR carries a focused set of Cloud Native Stack playbook improvements:

• Add enP* Calico interface autodetection for GB200-style NIC names.
• Make GPU Operator Helm installs retry-safe by switching from generated Helm
  release names to helm upgrade --install gpu-operator.
• Add Docker CE version and architecture variables, then use them in Ubuntu apt
  repository/package selection.
• Replace active Ubuntu apt_key usage with explicit keyring downloads/dearmor
  and signed-by apt repository handling.

Closes #140.

Motivation

These changes address issues found while validating newer NVIDIA systems and
newer Ubuntu runtimes:

• Some systems expose NIC names matching enP*, which were not covered by the
  existing Calico autodetection prefix list.
• helm install --generate-name is fragile in retry/reapply workflows because
  it can create duplicate generated releases or fail after partial installs.
• Docker CE package selection was unpinned and architecture was implicit, which
  can drift between reruns or mirrors.
• Newer Ubuntu images may not include apt-key, causing Ansible apt_key
  tasks to fail before repositories are configured.

Changes

1. Extend Calico autodetection from
   interface=ens*,eth*,enc*,bond*,enp*,eno* to include enP*.
2. Convert GPU Operator install paths to use a stable gpu-operator Helm
   release name with helm upgrade --install.
3. Add Docker CE versioning and apt architecture variables:
   • docker_ce_version
   • docker_ce_apt_version
   • docker_apt_arch
4. Replace active Ubuntu apt_key module usage with direct keyring management
   for Kubernetes, CRI-O, Docker, and NVIDIA Container Toolkit repositories.

Validation

Local validation passed for this patch series:

• git diff --check
• YAML parse checks for touched YAML files
• Ansible syntax checks for:
  • playbooks/prerequisites.yaml
  • playbooks/nvidia-driver.yaml
  • playbooks/nvidia-docker.yaml
  • playbooks/operators-install.yaml
  • playbooks/k8s-install.yaml
  • playbooks/cns.yaml

Maintainer Review Notes

• Please confirm whether gpu-operator is acceptable as the stable Helm
  release name.
• Please confirm Docker CE version defaults for CNS 16.0, 16.1, and 17.0.
• Please confirm the enP* Calico autodetection prefix matches expected GB200
  NIC naming.
• Please confirm keyring paths are acceptable:
  • /etc/apt/keyrings/kubernetes-apt-keyring.gpg
  • /etc/apt/keyrings/cri-o-apt-keyring.gpg
  • /etc/apt/keyrings/docker.asc
  • /usr/share/keyrings/nvidia-container-toolkit-keyring.gpg