ROX-35193: remove push-mode code and update CI for pull mode

[vikin91]

Description

📖 Design documentation: This PR is part of the VSOCK pull-mode feature. Before reviewing, please familiarize yourself with the architecture and protocol design in ADR-0006: VM Scanning VSOCK Pull Mode. This cleanup PR is straightforward, but the docs provide context for why the push-mode code is being removed.

Two things that go last in the stack:

Push-mode cleanup: Delete the old push-mode roxagent packages (index/, lock/, vsock/, common/config.go), the systemd timer, and strip push-mode logic from cmd.go.

CI/E2E updates: Deploy roxagent in serve mode and verify the pull flow end-to-end. Update Quadlet units for long-running pull-mode operation.

Deleted packages:

• compliance/virtualmachines/roxagent/common/ — push config
• compliance/virtualmachines/roxagent/index/ — push indexer loop
• compliance/virtualmachines/roxagent/lock/ — single-instance lock
• compliance/virtualmachines/roxagent/vsock/ — push VSOCK client
• scripts/ci/add-vms/systemd/roxagent.timer
• compliance/virtualmachines/roxagent/quadlet/roxagent.timer

User-facing documentation

• CHANGELOG.md is updated OR update is not needed
• documentation PR is created and is linked above OR is not needed

Testing and quality

• the change is production ready: the change is GA, or otherwise the functionality is gated by a feature flag
• CI results are inspected

Automated testing

• added unit tests
• added e2e tests
• added regression tests
• added compatibility tests
• modified existing tests

How I validated my change

TODO

[vikin91]

This change is part of the following stack:

• ROX-35191: expose RESTConfig on Sensor k8s client interface #21432
  • ROX-35189: Define protos for VSOCK pull between Sensor and roxagent #21433
    • ROX-35192: Add pull-mode VM scraper to Sensor #21434
      • ROX-35190: add pull-mode serve command to roxagent #21435
        • ROX-35193: remove push-mode code and update CI for pull mode #21436 ◀

_{Change managed by git-spice.}

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[github-actions]

🚀 Build Images Ready

Images are ready for commit 78d967b. To use with deploy scripts:

export MAIN_IMAGE_TAG=4.12.x-327-g78d967bcdf

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.10%. Comparing base (0c8035c) to head (78d967b).

Additional details and impacted files

@@                       Coverage Diff                        @@
##           piotr/ROX-35190-roxagent-serve   #21436    +/-   ##
================================================================
  Coverage                           50.10%   50.10%            
================================================================
  Files                                2842     2838     -4     
  Lines                              218305   217967   -338     
================================================================
- Hits                               109374   109208   -166     
+ Misses                             101002   100837   -165     
+ Partials                             7929     7922     -7     

Flag	Coverage Δ
go-unit-tests	50.10% <ø> (+<0.01%)	⬆️

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