[CASCL-1304] Add e2e assertion for dd-cluster-info ConfigMap

[L3n41c]

What does this PR do?

Adds a Verify dd-cluster-info ConfigMap sub-test to TestAutoscalingDefault
in test/e2e/tests/autoscaling_suite/autoscaling_test.go. The sub-test
fetches the dd-cluster-info ConfigMap that
kubectl datadog autoscaling cluster install writes in the dd-karpenter
namespace, unmarshals its YAML payload, and asserts every deterministic
field of the snapshot:

• ConfigMap metadata (name, namespace, app.kubernetes.io/managed-by label, data key).
• Schema version, ClusterName, ClusterARN (matched against a regex anchored
  on s.clusterName), Region, and a 30-minute freshness bound on GeneratedAt.
• NodeManagement.eksManagedNodeGroup contains exactly two entries whose
  names match the linux and linux-arm patterns provisioned by the
  e2e-framework.
• NodeManagement.fargate contains the install-time dd-karpenter-<cluster>
  profile, flagged as ManagedByDatadog.
• NodeManagement.karpenter is non-empty and every entry has the
  dd-karpenter- name prefix and ManagedByDatadog: true.
• Autoscaling.ClusterAutoscaler.Present == false, EKSAutoMode.Enabled == false,
  and Karpenter is present in dd-karpenter, named karpenter, with
  ManagedByDatadog, a populated InstallerVersion, and a SemVer-shaped
  Version.

The full YAML payload is logged unconditionally so any assertion failure
can be debugged from CI logs alone.

Motivation

PRs #2945 and #2980 introduced the dd-cluster-info ConfigMap as the source of truth consumed by the
follow-up Karpenter migration tool. No e2e coverage was asserting that
the ConfigMap actually gets written with the expected shape after a real
install on EKS. This adds that coverage as a sub-test of the existing
default install flow, so it shares the cluster provisioning and install
steps with the other autoscaling tests — no extra infrastructure cost.

Jira: CASCL-1304.

Additional Notes

The dd-cluster-info payload is unmarshaled into a locally-defined
wire-format struct rather than importing the producer's
cmd/kubectl-datadog/autoscaling/cluster/common/clusterinfo package, to
avoid pulling controller-runtime, karpenter, and the AWS autoscaling SDK
transitive dependencies into the e2e test module. The duplication is
documented and kept minimal.

Minimum Agent Versions

No agent-side change.

• Agent: N/A
• Cluster Agent: N/A

Describe your test plan

• The new sub-test runs as part of the existing autoscaling e2e suite on
  the EKS GitLab job; no new pipeline wiring required.
• Locally, the additions pass go vet, go build, and golangci-lint
  for the test/e2e module.
• The full ConfigMap YAML is logged via t.Logf so any future field
  drift surfaces directly in CI logs.

Checklist

• PR has at least one valid label: enhancement
• PR has a milestone or the qa/skip-qa label (qa/skip-qa: this is
  test-only and doesn't affect user-facing behavior)
• All commits are signed

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.50%. Comparing base (20ecb9e) to head (fad64b6).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3025   +/-   ##
=======================================
  Coverage   41.50%   41.50%           
=======================================
  Files         335      335           
  Lines       28714    28714           
=======================================
  Hits        11919    11919           
  Misses      16001    16001           
  Partials      794      794           

Flag	Coverage Δ
unittests	41.50% <ø> (ø)

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🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 41.82% (+0.00%)

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[L3n41c]

@codex review

[chatgpt-codex-connector]

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