[MCH] modify (pre)clustering workflows to process several ROF per TF

[pillot]

These modifications allow to send and process several events per time frame. Each individual interaction in the time frame is identified by an MCH ROF record, which contains the interaction record and the location of the associated objects (e.g. clusters) in the overall list.

@aphecetche @aferrero2707 I created a new PR because I messed-up the draft while trying to solve a conflict.

As we discussed, the modification of the preclustering workflow will temporarily break the linkup with the raw-to-digit workflow. My understanding is that we can go ahead with this PR and the linkup will fixed later on with the introduction of the temporal preclustering.

[aferrero2707]

@pillot yes, the ROF record introduced here is basically equivalent to the time-based clusters that are being introduced in #3644.
We will modify the time clustering so that it directly generates ROF records along with time-ordered vector of digits.