add: container test plugin for pytest

[realsdx]

Add a pytest based validation framework AzureLinux's OCI container images, integrated with azldev image test

Test it locally by (make sure to install and start podman first):

azldev image build container-base && azldev image test container-base

[Copilot]

Pull request overview

This PR extends Azure Linux’s image-test framework to support runtime validation of OCI container images (in addition to existing static/offline filesystem checks) and wires the new runtime suite into azldev image test.

Changes:

• Added --image-ref support (mutually exclusive with --image-path) and new pytest markers for runtime/container and Dockerfile-based tests.
• Introduced a python-on-whales/Podman-based container runtime helper plus session/function fixtures to run podman exec-style tests.
• Restructured test layout into cases/static/ vs cases/runtime/ and added an images.toml runtime test-suite for container-base variants.

Reviewed changes

Copilot reviewed 10 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
base/images/tests/utils/pytest_plugin.py	Adds --image-ref, new markers, and collection-time auto-marking for runtime/static test layout.
base/images/tests/utils/container_runtime.py	New Podman/python-on-whales orchestration helpers (load/pull/build/run/exec/cleanup).
base/images/tests/conftest.py	Adds runtime container fixtures (podman_client, running_container, container_exec, etc.) and supports --image-ref.
base/images/tests/README.md	Updates documentation to reflect static vs runtime suites and new CLI options/fixtures.
base/images/tests/pyproject.toml	Adds python-on-whales dependency for runtime container orchestration.
base/images/tests/cases/static/test_os_release.py	New shared static validation for /etc/os-release.
base/images/tests/cases/static/test_packages.py	New shared static RPM/package presence/absence checks (capability-gated).
base/images/tests/cases/static/vm-base/test_kernel.py	Adds VM kernel/modules checks and Fedora 43 CONFIG_LSM assertion.
base/images/tests/cases/static/vm-base/test_partitions.py	Adds VM partition layout checks (root + EFI).
base/images/tests/cases/static/container-base/test_container.py	Adds container static validation (no kernel modules).
base/images/tests/cases/runtime/container-base/test_basic.py	Adds basic runtime exec tests (shell + DNS).
base/images/tests/cases/runtime/container-base/test_nginx/*	Adds Dockerfile-based runtime example for nginx validation.
base/images/images.toml	Wires runtime-container-tests into container-base images and splits suite test-paths into cases/static/ and cases/runtime/.

Comments suppressed due to low confidence (1)

base/images/tests/utils/pytest_plugin.py:156

• pytest_configure derives image_type from --image-type, --capabilities, or --image-path, but it doesn’t consider --image-ref. When running with --image-ref and no --capabilities/--image-type, image_type stays None and check_tools(when=None) ends up requiring all tools (VM + container), which breaks the intended registry-ref workflow. Treat --image-ref as implying image_type="container" during this early preflight derivation.

    image_type = config.getoption("--image-type", default=None)
    if image_type is None:
        caps = parse_capabilities(config.getoption("--capabilities", default=None))
        if caps:
            image_type = derive_image_type_from_capabilities(caps)