MdeModulePkg: Add DxeResetSystemLib unit test

https://bugzilla.tianocore.org/show_bug.cgi?id=2505

* Add unit test of DxeResetSystemLib library
  instance that uses cmocka interfaces to mock the
  UEFI Runtime Services Table and its ResetSystem()
  service.  When a unit test uses the cmocka
  interfaces, the unit test does not support being
  run from target environments.

  cmocka APIs: https://api.cmocka.org/index.html

  This example puts the unit test in a UnitTest
  directory below the library INF file and this location
  means the unit test is only designed to work this
  this one library instance.

* Add Test/MdeModulePkgHostTest.dsc to build host
  based unit tests

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Acked-by: Hao A Wu <hao.a.wu@intel.com>
Reviewed-by: Bret Barkelew <Bret.Barkelew@microsoft.com>

MdeModulePkg/Library/DxeResetSystemLib/UnitTest/DxeResetSystemLibUnitTestHost.inf

@@ -0,0 +1,34 @@
+## @file
+# Unit tests of the DxeResetSystemLib instance of the ResetSystemLib class
+#
+# Copyright (C) Microsoft Corporation.
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010006
+  BASE_NAME                      = DxeResetSystemLibUnitTestHost
+  FILE_GUID                      = 83E35653-B943-4C5F-BA08-9B2996AE9273
+  MODULE_TYPE                    = HOST_APPLICATION
+  VERSION_STRING                 = 1.0
+
+#
+# The following information is for reference only and not required by the build tools.
+#
+#  VALID_ARCHITECTURES           = IA32 X64
+#
+
+[Sources]
+  DxeResetSystemLibUnitTest.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  UnitTestFrameworkPkg/UnitTestFrameworkPkg.dec
+
+[LibraryClasses]
+  ResetSystemLib
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  UnitTestLib