azure: Use IMDS attested metadata document for node identity

[hakman]

Replace the resourceID+vmID token with a PKCS7-signed attested metadata document from the Azure IMDS. The authenticator queries the attested document endpoint, and the verifier validates the PKCS7 signature chain, checks the nonce and expiration, then cross-verifies the signed vmId against the Azure API response.

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[hakman]

/test pull-kops-e2e-azure-cni-cilium

[k8s-ci-robot]

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[hakman]

/test pull-kops-e2e-azure-cni-cilium

[hakman]

/test pull-kops-e2e-azure-cni-cilium

[k8s-ci-robot]

@hakman: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kops-e2e-azure-cni-cilium	31832b8	link	true	/test pull-kops-e2e-azure-cni-cilium

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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