Currently our tests for the workload replayer don't seem to catch issues when we do not provide the map for the AddedByFileNum field in https://github.com/coolcom200/pebble/blob/b64a6d9dbe56640116108d37f2107f9b2601e3d0/replay/replay.go#L407. As a result we should write a test to ensure we test this codepath.

Related to: #2152 (review)

Jira issue: PEBBLE-165