UefiCpuPkg: add PcdGhcbHypervisorFeatures

UefiCpuPkg: add PcdGhcbHypervisorFeatures

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

Version 2 of the GHCB specification added a new VMGEXIT that the guest
could use for querying the hypervisor features. One of the immediate
users for it will be an AP creation code. When SEV-SNP is enabled, the
guest can use the newly added AP_CREATE VMGEXIT to create the APs.

The MpInitLib will check the hypervisor feature, and if AP_CREATE is
available, it will use it.

See GHCB spec version 2 for more details on the VMGEXIT.

Cc: Michael Roth <michael.roth@amd.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Ray Ni <ray.ni@Intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>