ci: add LVH-based integration tests for external contributors

[Molter73]

Description

Add a standalone GitHub Actions workflow that runs integration tests inside a nested QEMU/KVM VM using cilium/little-vm-helper (LVH). This enables external contributors (fork PRs) to run integration tests without requiring repository secrets or GCP credentials.

The workflow:

• Builds the fact container image locally (no registry push).
• Boots an LVH VM with a 6.6 LTS kernel and BPF LSM enabled via kernel cmdline.
• Loads the image into the VM's Docker and runs pytest against test_file_open.py as an initial spike validation.
• Caches the VM image and kernel for faster subsequent runs.
• Uses pull_request trigger (works for both fork and internal PRs).

This is Phase 1 (spike) of issue #1794. Once validated, Phase 2 will expand to the full test suite and Phase 3 will reduce duplication with the existing GCP VM-based integration tests.

Refs: #1794

Assisted-by: claude-opus-4-6 noreply@opencode.ai

Checklist

• Patch has a change log entry OR does not need one.
• Investigated and inspected CI test results
• Updated documentation accordingly

Automated testing

• Added unit tests
• Added integration tests
• Added regression tests

If any of these don't apply, please comment below.

Testing Performed

Validation needs to happen in CI.

[coderabbitai]

Important

Draft PR not reviewed

Draft PRs are not automatically reviewed by default.

• Trigger a manual review

To automatically review draft PRs, update your CodeRabbit configuration:

reviews:
  auto_review:
    drafts: true

---

_{Comment @coderabbitai help to get the list of available commands.}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 33.40%. Comparing base (05da053) to head (dc5d1fa).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1795   +/-   ##
=======================================
  Coverage   33.40%   33.40%           
=======================================
  Files          22       22           
  Lines        3628     3628           
  Branches     3628     3628           
=======================================
  Hits         1212     1212           
  Misses       2407     2407           
  Partials        9        9           

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