SecurityPkg: Implement AuthVariableLib library instance

SecurityPkg: Implement AuthVariableLib library instance

What to do:
1. Implement AuthVariableLib library instance.
2. Temporarily add VARIABLE_ENTRY_CONSISTENCY and
variable attribute combinations definitions to
AuthenticatedVariableFormat.h for git bisect.

Why to do:
1. Share code.
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.

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@17758 6f19259b-4bc3-4df7-8a09-765794883524