Include ID block when launching guests

An SEV-SNP "ID block" allows additional properties to be associated with/bound to an SEV-SNP CVM, for example, a "guest policy", a guest SVN and a Family ID. More guest tests are possible when SNP CVMs have these properties.

ID blocks need to be signed, but self-signing is allowed as the verifier checks the signature and the public key, which is included in the "ID authentication information structure". Both the ID block and the authentication information structure must be provided, for example, on the QEMU command line.

Note that ID blocks were introduced with SEV-SNP.