OvmfPkg/IntelTdx: Add SecTdxHelperLib

OvmfPkg/IntelTdx: Add SecTdxHelperLib

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

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

SecTdxHelperLib is the SEC instance of TdxHelperLib. It implements 4
functions for tdx in SEC phase:
 - TdxHelperProcessTdHob consumes TdHob to accept un-accepted memories.
   Before the TdHob is consumed, it is first validated.

 - TdxHelperMeasureTdHob measure/extend TdHob and store the measurement
   value in workarea.

 - TdxHelperMeasureCfvImage measure/extend the Configuration FV image and
   store the measurement value in workarea.

 - TdxHelperBuildGuidHobForTdxMeasurement builds GuidHob for tdx
   measurement.

This patch implements the stubs of the functions. The actual
implementations are in the following patches. Because they are moved from
other files.

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>