Integrate v0 trigger into the online processing chain

This MR integrates the V0 topology trigger into the online processing chain. The chosen method to do used minimal intervention to the existing code base and keeps backwards compatibility with the yaml configuration (EventBuildConfig.yaml). So, it the latter is untouched, the digi multiplicity trigger will be run as before.

To use the V0 trigger, the reconstruction (local reconstruction + tracking) has to be included in the chain. This is not yet automatized. In the configuration file, a node

v0trigger:
  max_time_diff: 50         /// time difference between two tracks in a pair
  min_z_pca: 1              /// minimum z position of point of closest approach
  max_dist_at_pca: 2        /// maximum distance between tracks at point of closest approach

has to added. If this node is found, the V0 trigger with the specified cut values will be applied instead of the digi multiplicity trigger.

In the process of implementing, I noticed that it seems approriate to restructure the entire online code to some extent, since the main steering class Reco becomes more and more spaghetti code. A more modular implementation, separating the trigger from the event builder step, is what I would like to have, but I did not want to introduce major re-arrangements of the code before the main mCBM data taking in May 2024.

EDIT PAL 24/04/2024: retarget to DC branch
EDIT PAL 25/04/2024: retarget to master as not ready to merge in time for DC#5 (will need a further rebase due to this)