MdePkg: Add RngLib into MdePkg

MdePkg: Add RngLib into MdePkg

Add one library class (RngLib.h) with three GetRandomNumber16/32/64
APIs to provide random number generator services, and one library
instance (BaseRngLib), based on Intel RdRand instruction access,
to provide high-quality random numbers generator.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qin Long <qin.long@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18519 6f19259b-4bc3-4df7-8a09-765794883524