CITest: Migrate G4ExHive test

Add the G4ExHive test to Athena and AthSimulation.

Relates to ATLINFR-4360. cc @jchapman @aundrus

AtlasTest/CITest/AthSimulation.cmake

-# Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
 #
 # CI test definitions for the AthSimulation project
 # --> README.md before you modify this file
@@ -8,6 +8,6 @@ atlas_add_citest( DuplicateClass
    SCRIPT python -c 'import ROOT'
    PROPERTIES FAIL_REGULAR_EXPRESSION "class .* is already in" )
 
-# TODO:
-#   G4ExHive
-#   SimulationTier0
+atlas_add_citest( G4ExHive
+   SCRIPT athena.py --threads=4 --evtMax=50 G4AtlasApps/jobOptions.G4AtlasMT.py
+   PROPERTIES PROCESSORS 4 )