Further implementation of Trigger ART python steering
This is a continuation of the effort started in !25314 (merged) and described in ATR-20038.
Further features implemented:
- Add more post-exec steps - RootComp, ChainDump, ZeroCounts, TrigTestJson, CheckFile
- Minor fixes / improvements
- Add basic unit test of the framework
The unit test is currently commented out because it fails due to ATEAM-562