UnitTestFrameworkPkg: Change target mode DebugLib mapping

UnitTestFrameworkPkg: Change target mode DebugLib mapping

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2801

The default DebugLib for target mode was DebugLibNull.  This
library instance disables all ASSERT() and DEBUG() macros
which removes the ability to write unit tests that check for
ASSERT() behaviors.

The DebugLib is changed to PeiDxeDebugLibReportStatusCode.inf
that guarantees that DEBUG() and ASSERT() macros are active.  The
default ReportStatusCodeLib is set to BaseReportStatusCodeLibNull.inf
so no messages are sent to any devices preserving the DebugLibNull
behavior.

A platform specific unit test can always override these mappings
with a platform specific DebugLib.

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Bret Barkelew <Bret.Barkelew@microsoft.com>