OvmfPkg: Prepare OvmfPkg to use the VmgExitLib library

OvmfPkg: Prepare OvmfPkg to use the VmgExitLib library

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

Various CpuExceptionHandlerLib libraries will updated to use the new
VmgExitLib library. To prevent any build breakage, update the OvmfPkg
DSC files that use a form of the CpuExceptionHandlerLib library to
include the VmgExitLib library.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>