end2end: add tests for workflow scripts with just dryrun enabled

[fnrizzi]

BEFORE this, we need to complete #27

ensure the workflow scripts execute the correct steps and product the correct dir structure.
To do this, for each driver script, we want to test various workflows by setting up combinations of workflow yaml files.
We can start from the yaml files arelady in the end-to-end-roms subdirs but need to test various combinations that exercise the workflow drivers properly.