UefiCpuPkg/SmmCpuFeaturesLib: Add Standalone MM support

UefiCpuPkg/SmmCpuFeaturesLib: Add Standalone MM support

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3218

Adds an INF for StandaloneMmCpuFeaturesLib, which supports building
the SmmCpuFeaturesLib code for Standalone MM. Minimal code changes
are made to allow reuse of existing code for Standalone MM.

The original INF file names are left intact (continue to use SMM
terminology) to retain backward compatibility with platforms that
use those INFs. Similarly, the pre-existing C file names are
unchanged to be consistent with the INF file names.

Note that all references in library source files to PiSmm.h have
been changed to PiMm.h for consistency.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Message-Id: <20210217213227.1277-6-mikuback@linux.microsoft.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>