OvmfPkg/IntelTdx: Add Sec to bring up both Legacy and Tdx guest

OvmfPkg/IntelTdx: Add Sec to bring up both Legacy and Tdx guest

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

OvmfPkg/IntelTdx/Sec is a simplied version of OvmfPkg/Sec. There
are below differences between these 2 Sec
 - IntelTdx/Sec only supports Legacy guest and Tdx guest in X64.
 - IntelTdx/Sec calls PeilessStartup () to jump from SEC to DXE directly.
 - IntelTdx/Sec uses MemoryAllocationLib / HobLib / PrePiLib in
   EmbeddedPkg.

Cc: Michael D Kinney <michael.d.kinney@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: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>