UefiCpuPkg: Extend VmgExitLibNull to handle #VE exception

UefiCpuPkg: Extend VmgExitLibNull to handle #VE exception

RFC： https://bugzilla.tianocore.org/show_bug.cgi?id=3429

VmgExitLib performs the necessary processing to handle a #VC exception.
VmgExitLibNull is a NULL instance of VmgExitLib which provides a
default limited interface. In this commit VmgExitLibNull is extended to
handle a #VE exception with a default limited interface. A full feature
version of #VE handler will be created later.

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: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>