UefiCpuPkg: Extend SMM CPU Service with rendezvous support.

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>