Michaelx/kata runtime snapshot endpoint + cli command

[michaelxu2288]

Merge Checklist

• Followed patch format from upstream recommendation: https://github.com/kata-containers/community/blob/main/CONTRIBUTING.md#patch-format
• Included a single commit in a given PR - at least unless there are related commits and each makes sense as a change on its own.
• Merged using "create a merge commit" rather than "squash and merge" (or similar)
• genPolicy only: Builds on Windows
• genPolicy only: Updated sample YAMLs' policy annotations, if applicable

Summary

Adds a kata-runtime snapshot subcommand to snapshot a
running Kata sandbox VM via cloud-hypervisor, plus a delete subcommand to remove a snapshot dir. Runs on the node:

kata-runtime snapshot --sandbox-id <sbid>           # take snapshot -> /run/vc/vm/snapshots/<sbid>/
kata-runtime snapshot --sandbox-id <sbid> --name X  # name the snapshot dir
kata-runtime snapshot delete --sandbox-id <sbid>    # remove a snapshot dir

The CLI POSTs to the per-sandbox shim management socket; the shim pauses the VM, saves kata state, snapshots VM memory + device state to the dir via SaveVM(path), then resumes. Built on top of Cameron's factory/hypervisor save-path refactor (this branch is stacked on guptaharshit/runtime-go-clh-templating).

Scope: snapshot-side only. Restore is performed manually with the CLH API for now (out of scope here).

Associated issues

Links to CVEs

N/A

Test Methodology

Local build (go build ./cmd/kata-runtime/... ./pkg/containerd-shim-v2/... ./virtcontainers/...) and full end-to-end on an AKS Azure Linux node (aks-nodepool1-23826427-vmss000000, MSHV + EROFS): snapshot a live pod at counter=5, restore into a fresh CLH process, confirm the clone resumes at counter=5 (live RAM inherited) and copy-on-write isolation holds (original stays 5 while clone advances to 7).

Full step-by-step e2e runbook attached: see nodepool0-snapshot-cli-e2e-runbook.md.nodepool0-snapshot-cli-e2e-runbook.md

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