refactor(swap_encryption/pr5): thin benchmark + remove duplicate phase logic

- Prepare() uses SwapNodePool + SwapDaemonSet from spec.resources
- Cleanup() is empty - PKB framework auto-deletes spec.resources
- All _pod_exec(pod, ...) calls replaced with daemonset.PodExec(...)
- Remove Phase 3a (Redis/memtier): duplicated kubernetes_redis_memtier_benchmark;
  run that benchmark on the swap-enabled cluster instead
- Remove Phase 3c (OpenSearch): fragile in-pod JVM launch; use esrally_benchmark
  on the swap-enabled cluster instead
- Keep Phase 3b (kernel build under cgroup memory cap): unique to this benchmark;
  kernel_compile_benchmark.py is VM-based and cannot run in a K8s pod
- Add _configure_eks_kubelet_swap() stub (deferred to PR #6780)
- Fix COS_CONTAINERD -> UBUNTU_CONTAINERD (r3472549985)

Author: DevVegeta