Likun/upf ws restore

[Liquidzk]

Summary

Follow-up to vhive-serverless#1221. This PR restores UPF working-set recording and replay.

Implementation Notes ⚒️

• Stores working-set pages and traces as snapshot artifacts.
• Installs the recorded working set during subsequent snapshot restores.
• Adds tests for recording and replaying working sets across different VM instances.

The legacy working-set design relied on VM-local in-memory state and did not fit revision-based restores. This implementation therefore:

• Stores artifacts by revision snapshot instead of VM ID.
• Persists versioned trace metadata for reuse across VM instances.
• Uses Firecracker mappings and page sizes for address translation.
• Validates and atomically replaces working-set artifacts.

External Dependencies 🍀

N/A

Breaking API Changes ⚠️

N/A