MdeModulePkg: Define the VariablePolicyLib

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

VariablePolicy is an updated interface to
replace VarLock and VarCheckProtocol.

Add the VariablePolicyLib library that implements
the portable business logic for the VariablePolicy
engine.

Also add host-based CI test cases for the lib.

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>

MdeModulePkg/Library/VariablePolicyLib/VariablePolicyExtraInitNull.c

@@ -0,0 +1,46 @@
+/** @file -- VariablePolicyExtraInitNull.c
+This file contains extra init and deinit routines that don't do anything
+extra.
+
+Copyright (c) Microsoft Corporation.
+SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/UefiRuntimeServicesTableLib.h>
+
+
+/**
+  An extra init hook that enables the RuntimeDxe library instance to
+  register VirtualAddress change callbacks. Among other things.
+
+  @retval     EFI_SUCCESS   Everything is good. Continue with init.
+  @retval     Others        Uh... don't continue.
+
+**/
+EFI_STATUS
+VariablePolicyExtraInit (
+  VOID
+  )
+{
+  // NULL implementation.
+  return EFI_SUCCESS;
+}
+
+
+/**
+  An extra deinit hook that enables the RuntimeDxe library instance to
+  register VirtualAddress change callbacks. Among other things.
+
+  @retval     EFI_SUCCESS   Everything is good. Continue with deinit.
+  @retval     Others        Uh... don't continue.
+
+**/
+EFI_STATUS
+VariablePolicyExtraDeinit (
+  VOID
+  )
+{
+  // NULL implementation.
+  return EFI_SUCCESS;
+}