which (tries to) maintain the number of successive visits resulting in the same status.
For example, if the last 3 visits are successful evenful ones, this field value will be
3. Then, an uneventful visit coming right after the latest eventful one will reset this
counter to one (last event is "uneventful" and only one such event happened
successively).
This will help when we will implement the disabling of too many failed visit attempt on
a given origin
Related to T2345
Depends on D5956
Supersedes D4895 (which I plan to commandeer and close)