Event-level report prioritization and deduplication interact unintuitively

[apasel422]

Consider the following scenario:

1. A source S is registered with max_event_level_reports = 1.
2. A trigger T1 with dedup key D1 and priority 100 is attributed to S, creating report R1.
3. A trigger T2 with dedup key D2 and priority 200 is attributed to S, causing R1 to be replaced with a new report R2.
4. A trigger T3 with dedup key D1 and priority 300 is attributed to S. No report is created, because the dedup key D1 is still associated with S.

This might be surprising behavior, as arguably D1 should have been deleted when R1 was.