MdeModulePkg: Define the VarCheckPolicyLib and SMM interface

MdeModulePkg: Define the VarCheckPolicyLib and SMM interface

https://bugzilla.tianocore.org/show_bug.cgi?id=2522

VariablePolicy is an updated interface to
replace VarLock and VarCheckProtocol.

This is an instance of a VarCheckLib that is backed by the
VariablePolicyLib business logic. It also publishes the SMM
calling interface for messages from the DXE protocol.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Bret Barkelew <brbarkel@microsoft.com>
Signed-off-by: Bret Barkelew <brbarkel@microsoft.com>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>
Acked-by: Jian J Wang <jian.j.wang@intel.com>