Significant MC Workflow restructuring

[sawenzel]

This is a bigger development related to https://its.cern.ch/jira/browse/O2-3622

It makes it possible to run embedding workflows with the --pregenCollContext feature. This means that the collision structure of all timeframes are now systematically generated before any event generation or GEANT transport stage.

The O2DPG MC workflows are restructured so that they

• generate the collision structure (collision context) at a very high level

  • this contains information about how collisions are composed (background-signal)
  • this also fixes the vertex of the collisions
  • this fixes the number of background and signal events to be generated
  • this is now done for all timeframes at once instead of in isolation (necessary to know how many background events are needed)

• thereafter we generate and transport background and signal events

This restructuring leads to more consistent workflow construction and smaller code. The old option --pregenCollContext is now the enforced default.

[github-actions]

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[alcaliva]

Hi @sawenzel,
when I try to port this PR for pbpb apass4 of 2023, I get conflicts (see below). What am I missing?
Alberto

DEBUG: git cherry-pick -x dbbf327
DEBUG: Auto-merging MC/bin/o2dpg_sim_workflow.py
DEBUG: CONFLICT (content): Merge conflict in MC/bin/o2dpg_sim_workflow.py
DEBUG: error: could not apply dbbf327... Significant MC Workflow restructuring (#1790)
DEBUG: hint: After resolving the conflicts, mark them with
DEBUG: hint: "git add/rm ", then run
DEBUG: hint: "git cherry-pick --continue".
DEBUG: hint: You can instead skip this commit with "git cherry-pick --skip".
DEBUG: hint: To abort and get back to the state before "git cherry-pick",
DEBUG: hint: run "git cherry-pick --abort".
DEBUG: git cherry-pick --abort
ERROR: There was a problem cherry-picking dbbf327