OvmfPkg/AmdSev: Enforce hash verification of kernel blobs

OvmfPkg/AmdSev: Enforce hash verification of kernel blobs

In the AmdSevX64 build, use BlobVerifierLibSevHashes to enforce
verification of hashes of the kernel/initrd/cmdline blobs fetched from
firmware config.

This allows for secure (measured) boot of SEV guests with QEMU's
-kernel/-initrd/-append switches (with the corresponding QEMU support
for injecting the hashes table into initial measured guest memory).

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>