MdePkg: Support mmio for Tdx guest in BaseIoLibIntrinsic

MdePkg: Support mmio for Tdx guest in BaseIoLibIntrinsic

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

TDVF access MMIO with TDG.VP.VMCALL to invoke VMM provided emulation
functions. If the access to MMIO fails, it fall backs to the direct
access.

BaseIoLibIntrinsic.inf is the IoLib used by other packages. It will
not support I/O in Td guest. But some files are shared between
BaseIoLibIntrinsic and BaseIoLibIntrinsicSev (IoLib.c is the example). So
IoLibInternalTdxNull.c (which holds the null stub of the Td I/O routines)
is included in BaseIoLibIntrinsic.inf. BaseIoLibIntrinsic.inf doesn't
import TdxLib so that the Pkgs which include BaseIoLibIntrinsic.inf
need not include TdxLib.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@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: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>