[BF-45928](https://jira.mongodb.org/browse/BF-45928) was triggered because of a specific case where the noop writer wasn't working but there was no pending work.

I originally went with the noop writer for simplicity of impl, but this is a more accurate way of checking idleness. Materialization lag implicitly checks for unmaterialized logs, so if we are stalled with no new logs coming out, and materialization is stalled we will crash