Backlog population is done by a linear scan separated by a 5 minute w…

[clemahieu]

…ait period. In this wait period and even while still scanning it's possible for the election scheduler to empty due to everything being confirmed faster than the scan can operate.

This should be rewritten to not scan at all and instead, a new database table can store the bucket/time as a key and when buckets are emptyied, it can be refilled directly from disk without scanning.