At the moment, a truncate operation, within the purview of a transaction, can generate enough dirty data in cache, that the cache becomes stuck full. The dirty content is almost exclusively on internal pages, so WiredTigers usual dirty-tracking machinery does not account for it.

We should extend dirty-usage tracking to work for optimized truncate, and introduce a limit for truncate transactions. This will cause a giant truncate to go from hanging indefinitely to returning a WT_ROLLBACK error.