refactor: rename the workflow element types

We should rename the workflow element types : https://gitlab.cta-observatory.org/cta-computing/dpps/workload/CTADIRAC/-/blob/main/src/CTADIRAC/ProductionSystem/Client/WorkflowElement.py?ref_type=heads#L31

So they are more readable, such as: mcsimulation -> mc_simulation , ctapipeprocessing -> ctapipe_processing

/cc @arrabito