Batch up DynamoDB updates for compaction job tracker

[patchwork01]

Background

Split from:

• Optimise job tracker updates on state store commits #3121

Description

We'd like to apply updates to the compaction job tracker in batches, rather than needing to apply them one at a time.

This should speed up tracking commits of finished compaction jobs.

Analysis

This is in DynamoDBCompactionJobTracker.

We can adjust the interface for CompactionJobTracker to be able to take a list of events, instead of just one at a time. Another alternative would be an implementation of CompactionJobTracker that gathers the events and has a separate method to commit the gathered events to DynamoDB.