OvmfPkg/IntelTdx: Add PeiTdxHelperLib

OvmfPkg/IntelTdx: Add PeiTdxHelperLib

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4243

TdxHelperLib provides below helper functions for a td-guest.
 - TdxHelperProcessTdHob
 - TdxHelperMeasureTdHob
 - TdxHelperMeasureCfvImage
 - TdxHelperBuildGuidHobForTdxMeasurement

PeiTdxHelperLib is the PEI instance of TdxHelperLib. It implements 1
function for tdx in PEI phase. Other functions are not supported in
PEI phase.
  - TdxHelperBuildGuidHobForTdxMeasurement builds GuidHob for tdx
    measurement in PEI phase.

Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>