MdePkg: implement MmServicesTableLib based on traditional SMM

MdePkg: implement MmServicesTableLib based on traditional SMM

The definitions of the rebranded MM protocol stack were chosen such
that the existing SMM based core drivers can be reused. So let's
implement MmServicesTableLib based on gEfiMmBaseProtocolGuid, which
is simply gEfiSmmBase2ProtocolGuid under the hood.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>