MdePkg/PciSegmentInfoLib: Add PciSegmentInfoLib class and instance.

MdePkg/PciSegmentInfoLib: Add PciSegmentInfoLib class and instance.

The patch adds PciSegmentInfoLib library class which is used
by PciSegmentLib (commit in next patch) to support multiple
segment PCI configuration access.

BasePciSegmentInfoLibNull instance is added but it shouldn't be
used by any real platform.
Any single segment platform that wants to use PciSegmentLib could
use BasePciSegmentLibPci instance.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>