UefiCpuPkg: Simplify InitializeSeparateExceptionStacks

UefiCpuPkg: Simplify InitializeSeparateExceptionStacks

Hide the Exception implementation details in CpuExcetionHandlerLib and
caller only need to provide buffer

Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>