systemc: Import tests from the Accellera systemc distribution.

Change-Id: Iad76b398949a55d768a34d027a2d8e3739953da6
Reviewed-on: https://gem5-review.googlesource.com/10845
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>