OvmfPkg: Copy Main.asm from UefiCpuPkg to OvmfPkg's ResetVector

OvmfPkg: Copy Main.asm from UefiCpuPkg to OvmfPkg's ResetVector

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

Previously OvmfPkg/ResetVector uses the Main.asm in
UefiCpuPkg/ReseteVector/Vtf0. In this Main.asm there is only Main16
entry point.

This patch-set is to introduce Intel TDX into Ovmf. Main32 entry point
is needed in Main.asm by Intel TDX. To reduce the complexity of Main.asm
in UefiCpuPkg, OvmfPkg create its own Main.asm to meet the requirement
of Intel TDX. This Main.asm is an unmodified copy (so no functional
change) and the actual changes for tdx come as incremental patches.

UefiCpuPkg/ResetVector/Vtf0/main.asm -> OvmfPkg/ResetVector/Main.asm

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.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>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>