MdeModulePkg: Add Variable Flash Info HOB

MdeModulePkg: Add Variable Flash Info HOB

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3479

Adds a new GUID that is used to identify a HOB that passes variable
flash information to UEFI variable drivers in HOB consumption phases
such as DXE, Traditional MM, and Standalone MM.

This information was previously passed directly with PCDs such
as EfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableBase
and gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize.

However, the Standalone MM variable driver instance does not have
direct access to the PCD database. Therefore, this HOB will first
be considered as the source for variable flash information and
if platforms do not produce the HOB, reading the information from
the PCDs directly will be a backup to provide backward
compatibility.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>