TriggerMenuMT: re-use runHLT in test_menu_CA

Re-use the default flags from runHLT in the test_menu_CA script. Also remove the use of an input file as the menu should not depend on it (ATR-27720).

Trigger/TriggerCommon/TriggerMenuMT/scripts/test_menu_CA.py

 #!/usr/bin/env python3
 # Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
 
-"""
-test of Dev menu with CA migrated menu code, reproducing runHLT_standalone_newJO
-"""
-from AthenaCommon.Logging import logging
-log = logging.getLogger('test_menu_CA')
+"""Standalone menu generation in CA mode"""
 
 from AthenaConfiguration.AllConfigFlags import initConfigFlags
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.AccumulatorCache import AccumulatorDecorator
+from TriggerJobOpts import runHLT
 
 # Make sure nobody uses deprecated global ConfigFlags
 import AthenaConfiguration.AllConfigFlags
 del AthenaConfiguration.AllConfigFlags.ConfigFlags
 
+# Set flags
 flags = initConfigFlags()
-
-# select chains, as in runHLT_standalone
-flags.addFlag("Trigger.enabledSignatures",[])
-flags.addFlag("Trigger.disabledSignatures",[])
-flags.addFlag("Trigger.selectChains",[])
-flags.addFlag("Trigger.disableChains",[])
-flags.Trigger.enabledSignatures = ['Muon', 'Photon','Electron', 'MinBias', 'HeavyIon', 'Jet', 'Tau', 'Bphysics', 'Egamma', 'MET', 'Bjet']
-# to be added after ATR-27632 fix: 'Calib']
-
+runHLT.set_flags(flags)
 flags.Trigger.generateMenuDiagnostics = True
+flags.Common.isOnline = True    # online environment
+flags.Input.Files = []          # menu cannot depend on input files
 
-from AthenaConfiguration.TestDefaults import defaultTestFiles
-flags.Input.Files = defaultTestFiles.RAW_RUN2
-flags.Trigger.triggerMenuSetup="Dev_pp_run3_v1"
-
-flags.Trigger.EDMVersion=3
 flags.fillFromArgs()
 flags.lock()
-flags.dump()
 
+# Set the Python OutputLevel on the root logger (usually done in MainServicesCfg)
+from AthenaCommon.Logging import log
+log.setLevel(flags.Exec.OutputLevel)
+
+from TriggerMenuMT.HLT.Config.GenerateMenuMT_newJO import generateMenuMT
 acc = ComponentAccumulator()
-from TriggerMenuMT.HLT.Config.GenerateMenuMT_newJO import generateMenuMT 
 menu = generateMenuMT(flags)
 acc.merge(menu)