MdeModulePkg Variable: Merge from Auth Variable driver in SecurityPkg

MdeModulePkg Variable: Merge from Auth Variable driver in SecurityPkg

What to do:
1. Merge from Auth Variable driver in SecurityPkg to Variable drive in
MdeModulePkg. Then the merged Variable driver in MdeModulePkg will
link to AuthVariableLib and TpmMeasurementLib.
AuthVariableLibNull and TpmMeasurementLibNull in MdeModulePkg
could be used for non auth variable support.
AuthVariableLib and DxeTpmMeasurementLib in SecurityPkg
may be used for auth variable support.

Why to do:
1. Remove code duplication and reduce maintenance effort.
After auth variable service separated from Auth Variable driver in SecurityPkg
to AuthVariableLib. The remaining code logic of Auth Variable driver in SecurityPkg
will be almost same with Variable driver in MdeModulePkg. Now it is to
merge them.

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@17765 6f19259b-4bc3-4df7-8a09-765794883524