MdePkg/BaseCpuLibNull: Add Null version of CpuLib for host testing

MdePkg/BaseCpuLibNull: Add Null version of CpuLib for host testing

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2798

The services in CpuLib usually generate exceptions in a unit test
host application.  Provide a Null instance that can be safely used.

This Null instance can also be used as a template for implementing
new instances of CpuLib.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Sean Brogan <sean.brogan@microsoft.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>