tools: support validating SEV firmware boot measurements

tools: support validating SEV firmware boot measurements

The virt-qemu-sev-validate program will compare a reported SEV/SEV-ES
domain launch measurement, to a computed launch measurement. This
determines whether the domain has been tampered with during launch.

This initial implementation requires all inputs to be provided
explicitly, and as such can run completely offline, without any
connection to libvirt.

The tool is placed in the libvirt-client-qemu sub-RPM since it is
specific to the QEMU driver.

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>