UefiCpuPkg: Implement library support for VMGEXIT

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

To support handling #VC exceptions and issuing VMGEXIT instructions,
create a library with functions that can be used to perform these
#VC/VMGEXIT related operations. This includes functions for:
  - Handling #VC exceptions
  - Preparing for and issuing a VMGEXIT
  - Performing MMIO-related write operations to support flash emulation
  - Performing AP related boot opeations

The base functions in this driver will not do anything and will return
an error if a return value is required. It is expected that other packages
(like OvmfPkg) will create a version of the library to fully support an
SEV-ES guest.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>