MdePkg: Add CcProbeLibNull

MdePkg: Add CcProbeLibNull

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3902

CcProbeLib is used to probe the Confidential Computing guest type.
This library is designed to run on SEC / PEI / DXE phases. A null
instance of the library always returns CCGuestTypeNonEncrypted.
A platform specific CcProbeLib will be implemented, for example,
in OvmfPkg.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>