OvmfPkg: Update PlatformInitLib to process Tdx hoblist

OvmfPkg: Update PlatformInitLib to process Tdx hoblist

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

When host VMM create the Td guest, the system memory informations are
stored in TdHob, which is a memory region described in Tdx metadata.
The system memory region in TdHob should be accepted before it can be
accessed. So the newly added function (ProcessTdxHobList) is to process
the TdHobList to accept the memory. Because TdHobList is provided by
host VMM which is not trusted, so its content should be checked before
it is consumed by TDVF.

Because ProcessTdxHobList is to be called in SEC phase, so
PlatformInitLib.inf is updated to support SEC.

Note: In this patch it is BSP which accepts the pages. So there maybe
boot performance issue. There are some mitigations to this issue, such
as lazy accept, 2M accept page size, etc. We will re-visit here in the
future.

EFI_RESOURCE_MEMORY_UNACCEPTED is a new ResourceType in
EFI_HOB_RESOURCE_DESCRIPTOR. It is defined for the unaccepted memory
passed from Host VMM. This is proposed in microsoft/mu_basecore#66
files#diff-b20a11152d1ce9249c691be5690b4baf52069efadf2e2546cdd2eb663d80c9
e4R237 according to UEFI-Code-First. The proposal was approved in 2021
in UEFI Mantis, and will be added to the new PI.next specification.

Per the MdePkg reviewer's comments, before this new ResourceType is
added in the PI spec, it should not be in MdePkg. So it is now
defined as an internal implementation and will be moved to
MdePkg/Include/Pi/PiHob.h after it is added in PI spec.
See https://edk2.groups.io/g/devel/message/87641

PcdTdxAcceptPageSize is added for page accepting. Currently TDX supports
4K and 2M accept page size. The default value is 2M.

Tdx guest is only supported in X64. So for IA32 ProcessTdxHobList
just returns EFI_UNSUPPORTED.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@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>