ci: fix CNI initialization failure in crictl e2e tests

[safiya2610]

Description

This PR fixes the failing crictl e2e tests in the CI pipeline where pods fail to create with the error: "cni plugin not initialized".

The issue started occurring because newer GitHub Action runner images (Ubuntu 22.04+) removed pre-installed tools like podman, which was inadvertently supplying the required CNI conflist that containerd was relying on.

To resolve this dependency on external environment factors, this PR updates the vm_test.yml workflow to explicitly write a default CNI bridge configuration file (10-containerd-net.conflist) into /etc/cni/net.d/ immediately after the CNI plugins are installed.

Related issues

• Fixes Crictl e2e tests fial in CI because cni plugin not initialize #967

How was this tested?

Verified by running the GitHub Actions CI pipeline (vm_test.yml) against this branch to ensure that containerd networking initializes correctly and the crictl e2e tests pass.

LLM usage

I used Google Gemini to help investigate the root cause in the GitHub Actions runner images, formulate the CNI configuration fix in vm_test.yml, and draft this pull request.

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

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[safiya2610]

@cmainas PTAL.