chore: update ACL os-release ID from 'acl' to 'azurecontainerlinux'

[aadhar-agarwal]

The acl-scripts repo changed the os-release ID from 'acl' to 'azurecontainerlinux'. Update all AgentBaker detection logic, VHD build config, and tests to match.

• Change ACL_OS_NAME constant from "ACL" to "AZURECONTAINERLINUX"
• Update sysext extension-release ID in acl-customdata.yaml/json
• Update direct $ID checks in init-aks-custom-cloud scripts
• Update e2e test to validate ID=azurecontainerlinux
• Regenerate snapshot testdata

[TEST All VHDs] AKS Linux VHD Build - https://msazure.visualstudio.com/CloudNativeCompute/_build/results?buildId=156027563&view=results

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

[Copilot]

Pull request overview

Updates Azure Container Linux (ACL) handling across AgentBaker to match upstream os-release ID change from acl to azurecontainerlinux, spanning provisioning scripts, VHD build inputs, and e2e/snapshot test artifacts.

Changes:

• Update ACL OS name/constants and distro detection to align with ID=azurecontainerlinux.
• Update ACL sysext extension-release metadata in Flatcar/Ignition customdata.
• Refresh e2e assertions and regenerated snapshot testdata to reflect the new ID.

Reviewed changes

Copilot reviewed 42 out of 82 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
vhdbuilder/packer/test/linux-vhd-content-test.sh	Updates ACL OS constant used by VHD content tests.
vhdbuilder/packer/post-install-dependencies.sh	Updates ACL OS constant for post-install logic.
vhdbuilder/packer/install-ig.sh	Updates ACL/Flatcar/Mariner skip condition to use constants.
vhdbuilder/packer/acl-customdata.yaml	Updates sysext extension-release ID to azurecontainerlinux.
vhdbuilder/packer/acl-customdata.json	Same as YAML, in JSON-encoded ignition payload.
pkg/agent/testdata/MarinerV2+Kata/CustomData	Regenerated snapshot test data (binary gzip payload).
pkg/agent/testdata/MarinerV2+CustomCloud/CustomData	Regenerated snapshot test data (binary gzip payload).
pkg/agent/testdata/CustomizedImageLinuxGuard/CustomData	Regenerated snapshot test data (binary gzip payload).
pkg/agent/testdata/CustomizedImageKata/CustomData	Regenerated snapshot test data (binary gzip payload).
pkg/agent/testdata/CustomizedImage/CustomData	Regenerated snapshot test data (binary gzip payload).
parts/linux/cloud-init/artifacts/init-aks-custom-cloud.sh	Updates /etc/os-release ID check for ACL detection.
parts/linux/cloud-init/artifacts/init-aks-custom-cloud-operation-requests.sh	Same ACL ID detection update.
parts/linux/cloud-init/artifacts/cse_helpers.sh	Updates ACL OS constant used by CSE helper logic.
e2e/scenario_test.go	Updates ACL e2e validation to expect ID=azurecontainerlinux.
e2e/config/vhd.go	Changes e2e OS selector value for ACL to azurecontainerlinux.
.pipelines/.vsts-vhd-builder-release.yaml	Updates SIG source image name/version used by ACL VHD build job.

[cameronmeissner]

/lgtm

[Copilot]

Pull request overview

Copilot reviewed 42 out of 82 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (2)

parts/linux/cloud-init/artifacts/init-aks-custom-cloud.sh:20

• This OS detection change drops support for older Azure Container Linux images that still report ID=acl in /etc/os-release. In that case, the script will hit the "Unknown Linux distribution" branch and exit 1, which can break custom-cloud initialization. Consider accepting both IDs (e.g., treat acl and azurecontainerlinux as ACL) during the 6‑month compatibility window, or add a clear migration guard/telemetry before removing the old value.

    elif [[ $ID == *"flatcar"* ]]; then
        IS_FLATCAR=1
    elif [[ $ID == "azurecontainerlinux" ]]; then
        IS_ACL=1
    else
        echo "Unknown Linux distribution"
        exit 1

parts/linux/cloud-init/artifacts/init-aks-custom-cloud-operation-requests.sh:20

• This OS detection change drops support for older Azure Container Linux images that still report ID=acl in /etc/os-release. If such an image runs this script, it will exit via the "Unknown Linux distribution" branch, potentially breaking operation-requests handling. Consider accepting both acl and azurecontainerlinux as ACL until older images are out of support.

    elif [[ $ID == *"flatcar"* ]]; then
        IS_FLATCAR=1
    elif [[ $ID == "azurecontainerlinux" ]]; then
        IS_ACL=1
    else
        echo "Unknown Linux distribution"
        exit 1

[Copilot]

Pull request overview

Copilot reviewed 42 out of 82 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (2)

parts/linux/cloud-init/artifacts/init-aks-custom-cloud.sh:20

• This OS detection only matches ID=azurecontainerlinux. For backward compatibility, older ACL images that still have ID=acl will hit the "Unknown Linux distribution" path and exit 1, breaking the custom-cloud init flow. Consider accepting both IDs (e.g., [[ $ID == "acl" || $ID == "azurecontainerlinux" ]]).

    elif [[ $ID == "azurecontainerlinux" ]]; then
        IS_ACL=1
    else
        echo "Unknown Linux distribution"
        exit 1

parts/linux/cloud-init/artifacts/init-aks-custom-cloud-operation-requests.sh:20

• This OS detection only matches ID=azurecontainerlinux. For backward compatibility, older ACL images that still have ID=acl will hit the "Unknown Linux distribution" path and exit 1, breaking the operation-requests init flow. Consider accepting both IDs (e.g., [[ $ID == "acl" || $ID == "azurecontainerlinux" ]]).

    elif [[ $ID == "azurecontainerlinux" ]]; then
        IS_ACL=1
    else
        echo "Unknown Linux distribution"
        exit 1

[Copilot]

Pull request overview

Copilot reviewed 42 out of 83 changed files in this pull request and generated no new comments.