Monitoring of HLT2 lines

We need to decide how to configure monitoring.

A first discussion was held today (2022-03-07) in https://indico.cern.ch/event/1118176/ (please see the slides). The feedback is that

Functor based monitoring exists already, see !1046 (merged) (thanks @mramospe)!
Flexibility to tailor monitoring to a given line is important, we should decide how to best express that without limiting ourselves.
We should implement automatic default monitoring of the final state (we don't want 500 MRs). Good general quantities to monitor are mass, pT, decay time, vertex chi2, eta.
This type of monitoring helps to catch line-specific issues early in the pit. It can also be useful when developing lines locally. It is not a substitute for producing ntuples offline and having more detailed studies (e.g. on correlations).