MdeModulePkg: Add VarCheckUefiLib NULL class library

MdeModulePkg: Add VarCheckUefiLib NULL class library

What to do: Implement VarCheckUefiLib NULL class library instance.
The code logic are separated from Variable driver, and it will consume VarCheckLib
to register var check handler and variable property set for UEFI defined variables.

Why to do: Share code.
Separate variable check UEFI code from Variable driver in MdeModulePkg.
We are going to separate generic software logic code from Variable Driver
to benefit other variable driver implementation. Auth services has been done
to be AuthVariableLib, now to cover variable check service.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18279 6f19259b-4bc3-4df7-8a09-765794883524