MdeModulePkg: Add SMBIOS 3.0 support in NetLibGetSystemGuid.

MdeModulePkg: Add SMBIOS 3.0 support in NetLibGetSystemGuid.

NetLibGetSystemGuid gets the UUID from SMBIOS table to use as the System GUID
(in DHCP and other network use cases). This change adds support to get the
UUID from either SMBIOS 2.x or 3.0, since SMBIOS 3.0 uses a different GUID in
the System Configuration Table.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Samer El-Haj-Mahmoud <samer.el-haj-mahmoud@hpe.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18559 6f19259b-4bc3-4df7-8a09-765794883524