MdeModulePkg: Move authenticated variable definition from SecurityPkg

MdeModulePkg: Move authenticated variable definition from SecurityPkg

What to do:
1. Move authenticated variable definition from AuthenticatedVariableFormat.h
to VariableFormat.h with gEfiAuthenticatedVariableGuid and
AUTHENTICATED_VARIABLE_HEADER.

Why to do:
1. Share code.
We are moving forward to 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.
2. 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. We are going to
merge them.
3. gEfiAuthenticatedVariableGuid will be used by both merged Variable driver
and AuthVariableLib, AUTHENTICATED_VARIABLE_HEADER will be used by
merged Variable driver.

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@17754 6f19259b-4bc3-4df7-8a09-765794883524