UefiCpuPkg: Extend SMM CPU Service with rendezvous support.

REF? https://bugzilla.tianocore.org/show_bug.cgi?id=3815

This patch define a new Protocol with the new services
SmmWaitForAllProcessor(), which can be used by SMI handler
to optionally wait for other APs to complete SMM rendezvous in
relaxed AP mode.

A new library SmmCpuRendezvousLib is provided to abstract the service
into library API to simple SMI handler code.

Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Zhihao Li <zhihao.li@intel.com>

Signed-off-by: Zhihao Li <zhihao.li@intel.com>

UefiCpuPkg/Library/SmmCpuRendezvousLib/SmmCpuRendezvousLib.inf

@@ -0,0 +1,35 @@
+## @file
+# SMM CPU Rendezvous service lib.
+#
+# This is SMM CPU rendezvous service lib that wait for all
+# APs to enter SMM mode.
+#
+# Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = SmmCpuRendezvousLib
+  FILE_GUID                      = 1509Bb36-9Ba4-438B-B195-Ac5914Db14E2
+  MODULE_TYPE                    = DXE_SMM_DRIVER
+  LIBRARY_CLASS                  = SmmCpuRendezvousLib|MM_STANDALONE DXE_SMM_DRIVER
+
+[Sources]
+  SmmCpuRendezvousLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  DebugLib
+  MmServicesTableLib
+
+[Pcd]
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmApSyncTimeout                 ## CONSUMES
+
+[Protocols]
+  gEdkiiSmmCpuRendezvousProtocolGuid