The event BOSS_KILL was introduced in Build 19445 as part of the "BossBanner" feature.
It has two known returns; id and name, but it is unknown what the id return actually represents.

If id is the same as in the EncounterJournal, we can ditch the current method of detecting the encounter, as well as the database of encounters, thus eliminating the need to update the addon every patch.

Turns out that the id parameter is the same as the one returned from ENCOUNTER_END, which is not something we can use.