ci: optimize self-hosted KubeVirt runners and CI pipeline

[mangelajo]

Summary

• Split KubeVirt runners into small (4Gi) and large (16Gi) VM flavors for better concurrency
• Route unit test / build jobs to arc-runner-kubevirt-small, E2E test jobs to arc-runner-kubevirt-large
• Run package tests in parallel (make test -j4 --output-sync on GNU Make, -j4 on BSD)
• Suppress log noise in CI with --log-level=CRITICAL --log-cli-level=CRITICAL via PYTEST_ADDOPTS (project defaults unchanged for local dev)
• Skip apt-get install when CI dependencies are already pre-baked in the golden image
• Increase Renode monitor connect timeout from 10s to 45s (smaller VMs need more startup time)
• Add download logging/timeout to u-boot test fixture for CI debuggability
• Detect --output-sync support via make --help instead of version string (works on macOS BSD make)

Test plan

• All python-tests matrix jobs pass (Linux small + macOS, Python 3.11/3.12/3.13)
• E2E tests pick up arc-runner-kubevirt-large label
• Log output is suppressed in CI but not locally
• macOS jobs run with -j4 without --output-sync (BSD make)
• Pre-baked dependencies skip apt-get install (check "Setup Linux dependencies" step)

🤖 Generated with Claude Code

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📝 Walkthrough

Walkthrough

This PR updates GitHub Actions workflow runner configurations across the E2E and Python test pipelines, migrating from ubuntu-24.04 to arc-runner-kubevirt for job execution while maintaining the existing matrix structures for architecture coverage.

Changes

Runner Infrastructure Migration

Layer / File(s)	Summary
E2E workflow jobs runner migration .github/workflows/e2e.yaml	Build controller and operator image jobs, build-python-wheels, e2e-tests, and compatibility jobs switch from ubuntu-24.04 to arc-runner-kubevirt in their job matrices and runner configurations.
Python tests workflow runner migration .github/workflows/python-tests.yaml	Pytest-matrix job updates its runs-on strategy from ubuntu-24.04 to arc-runner-kubevirt while retaining macos-15.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 In the CI clouds we hop and bound,
New runners found, a better ground,
Arc-runner-kubevirt, swift and true,
Let tests and builds run spry and new! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title 'ci: optimize self-hosted KubeVirt runners and CI pipeline' is partially related to the changeset, which focuses on switching to KubeVirt runners, but overstates the scope by claiming 'optimize CI pipeline' when the changes are primarily runner migrations.
Description check	✅ Passed	The PR description comprehensively aligns with the changeset, detailing infrastructure changes (KubeVirt runner migration), performance improvements (parallel testing), and CI optimizations (log suppression, timeout adjustments).

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch kubevirt-runners

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[kirkbrauer]

This looks good to me, hopefully we get quite a speedup here!

[mangelajo]

I am experimenting @kirkbrauer , the operator I am trying for the github actions in K8s + kubevirt seems to be a bit slow to rotate VMs, and grab jobs. Unless we get to improve that we would have to look for an alternative option