UnitTestFrameworkPkg: Add UnitTestPeiServicesTablePointerLib

This library supports a PeiServicesTablePointerLib implementation
that allows code dependent upon PeiServicesTable to operate in an
isolated execution environment such as within the context of a
host-based unit test framework.

The unit test should initialize the PeiServicesTable database with
any required elements (e.g. PPIs, Hob etc.) prior to the services
being invoked by code under test.

It is strongly recommended to clean any global databases by using
EFI_PEI_SERVICES.ResetSystem2 after every unit test so the tests
execute in a predictable manner from a clean state.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Michael Kubacki <mikuback@linux.microsoft.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>