MdeModulePkg: Add AuthVariableLib LibraryClass

MdeModulePkg: Add AuthVariableLib LibraryClass

What to do:
1. Add AuthVariableLib LibraryClass definitions.
2. Implement a NULL AuthVariableLib library instance.
3. Add VARIABLE_ENTRY_PROPERTY definition to VarCheck.h.
4. Add VARIABLE_ENTRY_CONSISTENCY and variable attribute
combinations definitions to VariableFormat.h.

Why to do:
1. Share code.
1.1. Separate auth variable service from Auth Variable driver in
SecurityPkg to AuthVariableLib. Then the AuthVariableLib could benefit
and be used by different implementation of Auth Variable drivers.

1.2 The VARIABLE_ENTRY_PROPERTY definition to VarCheck.h,
VARIABLE_ENTRY_CONSISTENCY and variable attribute
combinations definitions to VariableFormat.h will be shared
by merged Variable driver and AuthVariableLib.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17757 6f19259b-4bc3-4df7-8a09-765794883524