feat: Add VCPU type to GuestLaunchMeasurementMetadata

[frankdavid]

The PR adds a new field to GuestLaunchMeasurementMetadata to identify the VCPU type. In addition, it resolves an outstanding TODO to use named VCPU type for Turin. This is made possible by a recent change in the sev-snp-measure tool.

[github-actions]

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