Add option to run only one sig in new jo

In the mainline driving script, we have an option to run a fragment of the menu (e.g. Muons) for testing purposes. Now this is also possible in new JO. An example use:

python runHLT_standalone_newJO.py --filesInput=in.data Trigger.triggerMenuModifier="['emptyMenu','Muon','Electron']"

Related to https://its.cern.ch/jira/browse/ATR-19539

Trigger/TriggerCommon/TriggerJobOpts/python/TriggerConfigFlags.py

@@ -206,6 +206,10 @@ def createTriggerFlags():
     # name of the trigger menu
     flags.addFlag('Trigger.triggerMenuSetup', 'LS2_v1')
 
+    # modify the slection of chains that are run (default run all), see more in GenerateMenuMT_newJO
+
+    flags.addFlag('Trigger.triggerMenuModifier', ['all'])
+
     # name of the trigger menu
     flags.addFlag('Trigger.generateMenuDiagnostics', False)