webformnavigation_log becomes very large with no way to reduce its size

I think this could be like the webform draft purge configuration, where the admin defines a set number of days to purge drafts or completed webforms from the system. It does this when cron is run on the system. Would that make sense, or do you have other thoughts?

The byproduct of doing this will be that if a user visits a form whose logs have been removed, they will not see the pages that have errors or pages they have seen in the past in the navigation bar.

Another thought: what if we delete a submission's logs once the submission has been completed?