OvmfPkg: Refactor ProcessHobList

OvmfPkg: Refactor ProcessHobList

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

ProcessHobList once was implemented in PlatformInitLib and it walks thru
TdHob list and accept un-accepted memories.

This patch moves the codes to SecTdxHelperLib and rename ProcessHobList
as TdxHelperProcessTdHob

After TdxHelperProcessTdHob is introduced, below changes are applied:
 - Call TdxHelperProcessTdHob instead of ProcessHobList in SecMain.c
   (in both OvmfPkgX64/Sec and IntelTdx/Sec).
 - Delete the duplicated codes in PlatformInitLib

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>