sev/i386: qmp: add query-sev-launch-measure command
The command can be used by libvirt to retrieve the measurement of SEV guest.
This measurement is a signature of the memory contents that was encrypted
through the LAUNCH_UPDATE_DATA.
Cc: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>