When query is complete, load all logs and sort once

[eriktaubeneck]

Right now, log ordering is optimized for logs arriving async as they occur. However, when the query is complete, the arrival order tends to be grouped by servers (e.g., the fastest server provides all it's logs before the next server.)

The current system for handling that is inefficient in that scenario, and we can instead load all logs and sort once. We may even want to move this server side.

cc @akoshelev