Superevents should not have their preferred event change dynamically

The superevent manager updates the preferred event based on a criteria based on the event group, SNR, FAR. This is to be discontinued.

The proposed design change is as follows:

• The passing of should_publish adds the ADVREQ label to the superevent
• The completeness of a G event is determined by the presence of EMBRIGHT_READY, PASTRO_READY and SKYMAP_READY labels.

Pause updating preferred event

• The EM_SELECTED label is applied when the preferred_event of a superevent satisfies should_publish and it is complete i.e. S event has ADVREQ and preferred_event has EMBRIGHT_READY, PASTRO_READY and SKYMAP_READY labels.
• G event will continue to be added to S event until EM_SELECTED is applied after which point the preferred_event will not be updated. However, the time attributes of the superevents t_start, t_0 and t_end will continue to be updated.
• The placement of EM_SELECTED starts the preliminary alert pipeline with a first_preliminary_alert_timeout (=30s).
• The end of the preliminary alert pipeline applies the GCN_PRELIM_SENT.
• The GCN_PRELIM_SENT performs a clean up i.e. go over all G events added to the superevents since its locking and update the preferred event.
• There is a second_preliminary_alert_timeout (decide this timeout) to allow further addition of G event
• Repeat steps above with EM_SELECTED replaced with GCN_PRELIM_SENT