MdePkg: Add TdxLib to wrap Tdx operations

RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429

TdxLib is created with functions to perform the related Tdx operation.
This includes functions for:
 - TdAcceptPages   : Accept pending private pages and initialize the pages
                     to all-0 using the TD ephemeral private key.
 - TdExtendRtmr    : Extend measurement to one of the RTMR registers.
 - TdSharedPageMask: Get the Td guest shared page mask which indicates it
                     is a Shared or Private page.
 - TdMaxVCpuNum    : Get the maximum number of virtual CPUs.
 - TdVCpuNum       : Get the number of virtual CPUs.

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

MdePkg/MdePkg.dec

@@ -296,6 +296,9 @@
   ##  @libraryclass  Provides services to log the SMI handler registration.
   SmiHandlerProfileLib|Include/Library/SmiHandlerProfileLib.h
 
+  ##  @libraryclass  Provides function to support TDX processing.
+  TdxLib|Include/Library/TdxLib.h
+
 [Guids]
   #
   # GUID defined in UEFI2.1/UEFI2.0/EFI1.1