UnitTestFrameworkPkg/ResultReportLib: Remove invalid index string indicator

UnitTestFrameworkPkg/ResultReportLib: Remove invalid index string indicator

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2535

The UNIT_TEST_STATUS and FAILURE_TYPE have used 0 as status, so use 0 as
unknown is confused, remove it from array enumeration but keep it
location in the array.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Signed-off-by: Guomin Jiang <guomin.jiang@intel.com>
Reviewed-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com>