MdeModulePkg: Add VarCheckLib library

MdeModulePkg: Add VarCheckLib library

What to do:
1. Add VarCheckLib LibraryClass definitions.
2. Implement VarCheckLib library instance.
The code logic are separated from Variable driver.

Why to do: Share code.
Separate variable check service 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@18278 6f19259b-4bc3-4df7-8a09-765794883524