Switch default Windows image to windows-2022

[mboersma]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Updates CAPZ's in-tree Windows defaults from windows-2019 to windows-2022. Windows Server 2019 entered extended support in Jan 2024 and we no longer publish 2019 reference images, so any user creating an AzureMachine without explicitly setting windowsServerVersion would land on a stale, no-longer-published image.

CI scripts (scripts/ci-e2e.sh, ci-conformance.sh, ci-entrypoint.sh) already export WINDOWS_SERVER_VERSION="${WINDOWS_SERVER_VERSION:-windows-2022}" and the existing [REQUIRED] HA Windows worker e2e is consistently green at 2022, so the risk profile is low.

Changes:

• azure/defaults.go: DefaultWindowsGalleryImageName and DefaultWindowsOsAndVersion flipped to 2022
• azure/services/virtualmachineimages/images.go: the year-substitution in GetDefaultWindowsImage no longer assumes the default name contains "2019". Switched the brittle strings.Replace(imageName, "2019", match[1], 1) to regexp.ReplaceAllString(imageName, "\d{4}", match[1]), so any future default-year flip won't require touching this code again.
• test/e2e/helpers.go: the Windows version-intersection check in resolveKubernetesVersions now queries capi-win-2022-containerd (only runs when TEST_WINDOWS=true).

Intentionally not changed:

• The deprecated marketplace fallback path for old Kubernetes versions (oldWindows2019Versions map and the windows-2019-containerd-gen1 SKU) — those are hardcoded for k8s ≤ 1.28.12 etc. and reflect what was published to the Azure Marketplace at the time.
• Existing unit tests for windows-2019 osAndVersion in images_test.go and machine_test.go — they now serve as regression coverage for the explicit-override path.

Which issue(s) this PR fixes:
Fixes #5357

Special notes for your reviewer:

None.

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• cherry-pick candidate

Release note:

Switch default Windows image to windows-2022

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 43.95%. Comparing base (bd0f01b) to head (ca71a36).
⚠️ Report is 14 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6282   +/-   ##
=======================================
  Coverage   43.95%   43.95%           
=======================================
  Files         289      289           
  Lines       25351    25351           
=======================================
  Hits        11143    11143           
  Misses      13435    13435           
  Partials      773      773           

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[mboersma]

/test pull-cluster-api-provider-azure-conformance-with-ci-artifacts

[willie-yao]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Details

Git tree hash: ce523f30bd4691bc4c79ea1eb5ca0e98041a5a64

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: willie-yao

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